The compiler doesn't know that `32` is an offset into the Hash table:

 56 struct Hash_ctx {
 57         u8 H[16];       /* subkey */
 58         u8 Htable[256]; /* Xi, Hash table(offset 32) */
 59 };

So, it legitimately complains about a potential out-of-bounds issue
if `256 bytes` are accessed in `htable` (this implies going
`32 bytes` beyond the boundaries of `Htable`):

arch/powerpc/crypto/aes-gcm-p10-glue.c: In function 'gcmp10_init':
arch/powerpc/crypto/aes-gcm-p10-glue.c:120:9: error: 'gcm_init_htable' accessing 256 bytes in a region of size 224 [-Werror=stringop-overflow=]
  120 |         gcm_init_htable(hash->Htable+32, hash->H);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/powerpc/crypto/aes-gcm-p10-glue.c:120:9: note: referencing argument 1 of type 'unsigned char[256]'
arch/powerpc/crypto/aes-gcm-p10-glue.c:120:9: note: referencing argument 2 of type 'unsigned char[16]'
arch/powerpc/crypto/aes-gcm-p10-glue.c:40:17: note: in a call to function 'gcm_init_htable'
   40 | asmlinkage void gcm_init_htable(unsigned char htable[256], unsigned char Xi[16]);
      |                 ^~~~~~~~~~~~~~~

Address this by avoiding specifying the size of `htable` in the function
prototype; and just for consistency, do the same for parameter `Xi`.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/linux-next/20231121131903.68a37932@canb.auug.org.au/Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>