Add license identifier to files which Arm owns the copyright to,
and contain either BSD-3 or Apache-2.0 licenses. This is to address
license errors raised by scancode analysis.
- Move back the 16/32bit timer initialization in HAL_InitTick() and not in us_ticker_init()
- Use ticker_read_us() and us_ticker_read() in HAL_GetTick() to fix potential overflow issue with the 16bit timer
==> These corrections allow timer, rtc, sleep, tick tests to PASS