STM32 LPTICKER with LPTIM : reduce clock feature

[jeromecoutant]

Description

This fix follows #7156 (comment)
@rohithreddykota-npsc

Default behavior is not changed : Frequency is 32768 Hz with a 16 bits timer
This provides:

• a 30us precision
• and a sleep time about 2s

You have now the possibility to divide frequency by 4

• Precision becomes around 132us
• Sleep time is now about 8s

Add:

• in targets.json file:
  "overrides": { "lpticker_lptim_clock": 4 },

• in your local mbed_app.json file:
  "target_overrides": {
  xxx
  "target.lpticker_lptim_clock": 4

@c1728p9 @LMESTM

Pull request type

[ ] Fix
[x] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3651
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8778/

Triggering tests

/morph test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : FAILURE

Build number : 3258
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8778/

[mbed-ci]

Test : SUCCESS

Build number : 3431
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8778/3431

[0xc0170]

Trying to make this to pass alone rather

/morph export-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 3275
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8778/