crypto: arm64/sha2-ce - move the round constant table to .rodata section

Move the SHA2 round constant table to the .rodata section where it is
safe from being exploited by speculative execution.

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