aarch64: Enable use of SME by EL2 and below

Allow lower ELs to use SME when booted on a system that support it. This
requires us to set two new bits, one in each of SCR_EL3 and CPTR_EL3, set
the maximum vector length in a similar fashion to SVE and if the optional
FA64 feature is present then set another feature bit in the new SMCR
register.

Signed-off-by: Mark Brown <broonie@kernel.org>
[Mark R: use BIT() for ID_AA64SMFR0_EL1_FA64, sort ID_AA64PFR1_EL1 fields]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20220201172132.2399026-2-broonie@kernel.org
2 files changed