MCU_LPC546XX: libpower lib needs readme and license

[0xc0170]

Description

Tracking issue for missing readme and license file for libpower.a files for MCU_LPC546XX target. Already discussed in pull request that brought this, creating this so we do not forget to add these files

@ARMmbed/team-nxp

Issue request type

[ ] Question
[ ] Enhancement
[X] Bug

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-383

[0xc0170]

Fixed via #9360