lib/crc: make arch-optimized code use subsys_initcall

Make the architecture-optimized CRC code do its CPU feature checks in
subsys_initcalls instead of arch_initcalls.  This makes it consistent
with arch/*/lib/crypto/ and ensures that it runs after initcalls that
possibly could be a prerequisite for kernel-mode FPU, such as x86's
xfd_update_static_branch() and loongarch's init_euen_mask().

Note: as far as I can tell, x86's xfd_update_static_branch() isn't
*actually* needed for kernel-mode FPU.  loongarch's init_euen_mask() is
needed to enable save/restore of the vector registers, but loongarch
doesn't yet have any CRC or crypto code that uses vector registers
anyway.  Regardless, let's be consistent with arch/*/lib/crypto/ and
robust against any potential future dependency on an arch_initcall.

Link: https://lore.kernel.org/r/20250510035959.87995-1-ebiggers@kernel.org


Signed-off-by: Eric Biggers <ebiggers@google.com>