kselftest/arm64: add DEF_SIGHANDLER_FUNC() and DEF_INST_RAISE_SIG() helpers

Add macro definition functions DEF_SIGHANDLER_FUNC() and
DEF_INST_RAISE_SIG() helpers.

Furthermore, there is no need to modify the default SIGILL handling
function throughout the entire testing lifecycle in the main() function.
It is reasonable to narrow the scope to the context of the sig_fn
function only.

This is a pre-patch for the subsequent SIGBUS handler patch.

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230808134036.668954-4-zengheng4@huawei.com


Signed-off-by: Will Deacon <will@kernel.org>