Update Mbed OS to 6.11.0

[gpsimenos]

Build successes:
  * K64F::GCC_ARM::MBED-BUILD
  * K64F::GCC_ARM::TESTS-API-DIGITALIO
  * K64F::GCC_ARM::TESTS-ASSUMPTIONS-ANALOGIN
  * K64F::GCC_ARM::TESTS-ASSUMPTIONS-ANALOGOUT
  * K64F::GCC_ARM::TESTS-ASSUMPTIONS-DIGITALIO
  * K64F::GCC_ARM::TESTS-ASSUMPTIONS-I2C
  * K64F::GCC_ARM::TESTS-ASSUMPTIONS-PWM
  * K64F::GCC_ARM::TESTS-ASSUMPTIONS-SPI

[MarceloSalazar]

@ARMmbed/team-st-mcd would you like to test a few of your boards with Mbed OS 6 and provide feedback?

[jeromecoutant]

I started from a clean view.
This patch set "latest" label in mbed-os which is mbed-os-5.15.1 :-(

[jeromecoutant]

After a manual checkout mbed-os-6.4.0,
I add #44 which is still missing in master

Then compilation with ARM is OK except few warnings:

[Warning] PWM_rise_fall.cpp@77,31: 'read_us' is deprecated: Use the Chrono-based elapsed_time method.  If integer microseconds are needed, you can use `elapsed_time().count()` [since mbed-os-6.0.0] [-Wdeprecated-declarations]
[Warning] PWM_rise_fall.cpp@89,59: 'read_us' is deprecated: Use the Chrono-based elapsed_time method.  If integer microseconds are needed, you can use `elapsed_time().count()` [since mbed-os-6.0.0] [-Wdeprecated-declarations]
[Warning] SPI.cpp@96,39: format string is not a string literal (potentially insecure) [-Wformat-security]
[Warning] Comms.cpp@96,31: format string is not a string literal (potentially insecure) [-Wformat-security]
[Warning] Comms.cpp@161,31: format string is not a string literal (potentially insecure) [-Wformat-security]
[Warning] Mixed.cpp@99,31: format string is not a string literal (potentially insecure) [-Wformat-security]
[Warning] Mixed.cpp@282,35: format string is not a string literal (potentially insecure) [-Wformat-security]

[jeromecoutant]

GCC warnings:

[Warning] BusInOut.cpp@29,9: variable 'x' set but not used [-Wunused-but-set-variable]
[Warning] I2C.cpp@94,9: variable 'r' set but not used [-Wunused-but-set-variable]
[Warning] I2C.cpp@95,9: variable 'w' set but not used [-Wunused-but-set-variable]
[Warning] PWM_rise_fall.cpp@77,39: 'int mbed::TimerBase::read_us() const' is deprecated: Use the Chrono-based elapsed_time method.  If integer microseconds are needed, you can use `elapsed_time().count()` [since mbed-os-6.0.0] [-Wdeprecated-declarations]
[Warning] PWM_rise_fall.cpp@89,67: 'int mbed::TimerBase::read_us() const' is deprecated: Use the Chrono-based elapsed_time method.  If integer microseconds are needed, you can use `elapsed_time().count()` [since mbed-os-6.0.0] [-Wdeprecated-declarations]
[Warning] PWM_rise_fall.cpp@122,9: unused variable 'one_percent' [-Wunused-variable]
[Warning] SPI.cpp@86,9: variable 'error' set but not used [-Wunused-but-set-variable]
[Warning] SPI.cpp@110,9: variable 'error' set but not used [-Wunused-but-set-variable]

[gpsimenos]

Thanks @jeromecoutant for testing with mbed os 6.4.0. Will update the patch.

[0xc0170]

@gpsimenos Still worth updating to the recent Mbed OS version?

[jeromecoutant]

Note goal of this PR should be not to update mbed-os version... but to remove deprecated API and match the latest standard...