Disable LSE for MTB_USI_WM_BN_BM_22

[kivaisan]

Description

Current MTB_USI_WM_BN_BM_22 modules do not have OSC32_IN connected, so
external xtal is not in use.

Pull request type

[X] Fix
[ ] Refactor
[ ] New target
[ ] Feature
[ ] Breaking change

[kivaisan]

This fixes #6591 for MTB_USI_WM_BN_BM_22 target.

[ashok-rao]

Thanks @kivaisan ..

1. I think this will also be the case for MTB_ADV_WISE_1530 as well. Can you please check the schematics for 1530 and move this to the parent target if suitable?
2. Minor nit on coding standards.. can you please follow coding conventions for 1 statement per line?

[kivaisan]

@ashok-rao WISE-1530 RTC tests (atleast the ones reported in MBEDOSTEST-24) works ok with LSE. And according to its datasheet, it should have the external xtal installed. Therefore I wouldn't put the setting to parent but just to module specific configuration.
Also modified the commit to follow coding standards.

[ashok-rao]

LGTM! Thanks @kivaisan

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2565
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7446/

Triggering tests

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

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2209
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7446/

[mbed-ci]

Test : SUCCESS

Build number : 2319
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7446/2319