Add a new option, -mfix-cmse-cve-2021-35465 and document it. Enable it
automatically for cortex-m33, cortex-m35p and cortex-m55.
gcc:
PR target/102035
* config/arm/arm.opt (mfix-cmse-cve-2021-35465): New option.
* doc/invoke.texi (Arm Options): Document it.
* config/arm/arm-cpus.in (quirk_vlldm): New feature bit.
(ALL_QUIRKS): Add quirk_vlldm.
(cortex-m33): Add quirk_vlldm.
(cortex-m35p, cortex-m55): Likewise.
* config/arm/arm.c (arm_option_override): Enable fix_vlldm if
targetting an affected CPU and not explicitly controlled on
the command line.