module/icp/asm-arm/sha2: enable non-SIMD asm kernels on armv5/6

[Harry-Chen]

Motivation and Context

My merged pull request #15557 fixes compilation of sha2 kernels on arm v5/6.

However, the compiler guards only allow sha256/512_armv7_impl to be used when __ARM_ARCH > 6. Therefore old arm architectures cannot leverage the well-written asm kernels zfs_sha256/512_block_armv7 (from openssl project) and always fall back to the generic C implementation. This might lead to unnecessary performance degradation.

These kernels are actually named armv4 from the openssl side. So I believe it has been guaranteed to work on old arm arches.

Description

This patch enables these ASM kernels on all arm architectures. Some compiler guards are adjusted accordingly to avoid the unnecessary compilation of SIMD (e.g., neon, armv8ce) kernels on old architectures.

See also: 4c5fec0

How Has This Been Tested?

I have tested compilation on armv5te / armv6 architectures. No behavior changes are made to other architectures.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[behlendorf]

Thanks.