kselftest/arm64: Correct misleading comments on fp-stress irritators

The comments in the handlers for the irritator signal in the test threads
for fp-stress suggest that the irritator will corrupt the register state
observed by the main thread but this is not the case, instead the FPSIMD
and SVE irritators (which are the only ones that are implemented) modify
the current register state which is expected to be overwritten on return
from the handler by the saved register state. Update the comment to reflect
what the handler is actually doing.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241107-arm64-fp-stress-irritator-v2-1-c4b9622e36ee@kernel.org


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