STM32_gen_PeripheralPins.py, V1.20 doesn't work with -m option

[leichunyang]

mbed-os\targets\TARGET_STM\tools\STM32_gen_PeripheralPins.py,
V1.20 doesn't work with -m options.

[ciarmcom]

@leichunyang This issue has an incomplete or old issue template.For future reference please use an up to date clone of the repository before raising issues. Many thanks.

[ciarmcom]

Thank you for raising this detailed GitHub issue. I am now notifying our internal issue triagers.
Internal Jira reference: https://jira.arm.com/browse/IOTOSM-3858

[0xc0170]

@ARMmbed/team-st-mcd Please review

[jeromecoutant]

Good catch!

Please check #14594