STM32 USB : Add __HAL_RCC_PWR_CLK_ENABLE

[jeromecoutant]

Description

USB tests are failed within the master branch

Summary of change

Miss to enable one clock during #11675

Documentation

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Pull request type

[x] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

| DISCO_L475VG_IOT01A-ARMC6 | DISCO_L475VG_IOT01A | tests-usb_device-hid | OK | 25.34 | default |

[] No Tests required for this change (E.g docs only update)
[x] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers

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Release Notes

Summary of changes

Impact of changes

Migration actions required

[ciarmcom]

@jeromecoutant, thank you for your changes.
@ARMmbed/mbed-os-maintainers please review.

[0xc0170]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 1
Build artifacts