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.
pwmout:
Used SystemCoreClock
Serial fuart:
SERIAL_5 & SERIAL_3 have same CTS pin (PA7), only function register is different (4 & 2).
pinmap_peripheral() will always return first match from the map.
Hence changed as, if SERIAL_5 is used, then pinmap_peripheral() should return SERIAL_5 (function register 2 to be set).