arm64: Add the arm64.nosve command line option

In order to be able to completely disable SVE even if the HW
seems to support it (most likely because the FW is broken),
move the SVE setup into the EL2 finalisation block, and
use a new idreg override to deal with it.

Note that we also nuke id_aa64zfr0_el1 as a byproduct, and
that SME also gets disabled, due to the dependency between the
two features.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220630160500.1536744-9-maz@kernel.org


Signed-off-by: Will Deacon <will@kernel.org>