crypto: arm64/poly1305 - move data to rodata section

When objtool gains support for ARM in the future, it may encounter issues
disassembling the following data in the .text section:
> .Lzeros:
> .long   0,0,0,0,0,0,0,0
> .asciz  "Poly1305 for ARMv8, CRYPTOGAMS by \@dot-asm"
> .align  2

Move it to .rodata which is a more appropriate section for read-only data.

There is a limit on how far the label can be from the instruction, hence
use "adrp" and low 12bits offset of the label to avoid the compilation
error.

Signed-off-by: Jia He <justin.he@arm.com>
Tested-by: Daniel Gomez <da.gomez@samsung.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>