arm64: sysreg: replace open-coded mrs_s/msr_s with {read,write}_sysreg_s
Similar to our {read,write}_sysreg accessors for architected, named
system registers, this patch introduces {read,write}_sysreg_s variants
that can take arbitrary sys_reg output and therefore access IMPDEF
registers or registers that unsupported by binutils.
Reviewed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>