crypto: arm/crc32 - fix build error with outdated binutils

Annotate a vmov instruction with an explicit element size of 32 bits.
This is inferred by recent toolchains, but apparently, older versions
need some help figuring this out.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>