Patch is adding Cortex-R52+ as 'cortex-r52plus' command line
flag for -mcpu option.

See: https://www.arm.com/products/silicon-ip-cpu/cortex-r/cortex-r52-plus

OK for master?

gcc/ChangeLog:

2021-09-22  Przemyslaw Wirkus  <przemyslaw.wirkus@arm.com>

	* config/arm/arm-cpus.in: Add Cortex-R52+ CPU.
	* config/arm/arm-tables.opt: Regenerate.
	* config/arm/arm-tune.md: Regenerate.
	* doc/invoke.texi: Update docs.