kselftest/arm64: Check that SVCR is 0 in signal handlers

kselftest/arm64: Check that SVCR is 0 in signal handlers

We don't currently validate that we exit streaming mode and clear ZA when
we enter a signal handler. Add simple checks for this in the SSVE and ZA
tests.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241106-arm64-fpmr-signal-test-v1-1-31fa34ce58fe@kernel.org
[catalin.marinas@arm.com: Use %lx in fprintf() as uint64_t seems to be unsigned long in glibc]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>