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>

tools/testing/selftests/arm64/fp/fpsimd-test.S

@@ -134,8 +134,7 @@ function check_vreg
 	b	memcmp
 endfunction
 
-// Any SVE register modified here can cause corruption in the main
-// thread -- but *only* the registers modified here.
+// Modify live register state, the signal return will undo our changes
 function irritator_handler
 	// Increment the irritation signal count (x23):
 	ldr	x0, [x2, #ucontext_regs + 8 * 23]

tools/testing/selftests/arm64/fp/sve-test.S

@@ -291,8 +291,7 @@ function check_ffr
 #endif
 endfunction
 
-// Any SVE register modified here can cause corruption in the main
-// thread -- but *only* the registers modified here.
+// Modify live register state, the signal return will undo our changes
 function irritator_handler
 	// Increment the irritation signal count (x23):
 	ldr	x0, [x2, #ucontext_regs + 8 * 23]