arm64/signal: Clean up SVE/SME feature checking inconsistency

arm64/signal: Clean up SVE/SME feature checking inconsistency

Currently when restoring signal state we check to see if SVE is supported
in restore_sigframe() but check to see if SVE is supported inside
restore_sve_fpsimd_context(). This makes no real difference since SVE is
always supported in systems with SME but looks a bit untidy and makes
things slightly harder to follow, move the SVE check next to the SME one
in restore_sve_fpsimd_context().

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220624172108.555000-1-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>