In order to feal with early override of features that are not
classically encoded in a standard ID register with a 4 bit wide
field, add a primitive that takes a sysreg value as an input
(instead of the usual sysreg name) as well as a bit field
width (usually 4).

No functional change.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220630160500.1536744-7-maz@kernel.orgSigned-off-by: Will Deacon <will@kernel.org>