kselftest/arm64: Add HWCAP test for FEAT_LS64

kselftest/arm64: Add HWCAP test for FEAT_LS64

Add tests for FEAT_LS64. Issue related instructions if feature
presents, no SIGILL should be received. When such instructions
operate on Device memory or non-cacheable memory, we may received
a SIGBUS during the test (w/o FEAT_LS64WB). Just ignore it since
we only tested whether the instruction itself can be issued as
expected on platforms declaring the support of such features.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Oliver Upton <oupton@kernel.org>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
Signed-off-by: Will Deacon <will@kernel.org>