arm: Add support for Arm Cortex-M85 CPU.

arm: Add support for Arm Cortex-M85 CPU.

This patch adds the -mcpu support for the Arm Cortex-M85 CPU which is
an Armv8.1-M Mainline CPU supporting MVE and PACBTI by default.

-mpcu=cortex-m85 switch by default matches to -march=armv8.1-m.main+pacbti+mve.fp+fp.dp.

Also following options are provided to disable default features.
+nomve.fp (disables MVE Floating point)
+nomve (disables MVE Integer and MVE Floating point)
+nodsp (disables dsp, MVE Integer and MVE Floating point)
+nopacbti (disables pacbti)
+nofp (disables floating point and MVE floating point)

gcc/ChangeLog:

2022-08-12  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

	* config/arm/arm-cpus.in (cortex-m85): Define new CPU.
	* config/arm/arm-tables.opt: Regenerate.
	* config/arm/arm-tune.md: Likewise.
	* doc/invoke.texi (Arm Options): Document -mcpu=cortex-m85.
	* (-mfix-cmse-cve-2021-35465): Likewise.

gcc/testsuite/ChangeLog:

2022-08-12  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

	* gcc.target/arm/multilib.exp: Add tests for cortex-m85.