arm64: Explicitly require that FPSIMD instructions do not trap

We do not explicitly require that systems with FPSIMD support and EL3 have
disabled EL3 traps when the kernel is started, while it is unlikely that
systems will get this wrong for the sake of completeness let's spell it
out.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210412151955.16078-3-broonie@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>