Hi,

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)

Regression tested on arm-none-eabi and bootstrapped on arm-none-linux-gnueabihf.

Ok for master?

Regards,
Srinath.

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.