selftests/arm64: add HWCAP2_HBC test

Add a test for the newly added HWCAP2_HBC.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230804143746.3900803-3-joey.gouly@arm.com


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