kselftest/arm64: add jscvt feature to hwcap test

Add the jscvt feature check in the set of hwcap tests.

Due to the requirement of jscvt feature, a compiler configuration
of v8.3 or above is needed to support assembly. Therefore, hand
encode is used here instead.

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230815040915.3966955-5-zengheng4@huawei.com


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