crypto: p10-aes-gcm - Avoid -Wstringop-overflow warnings

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 <[e-mail]>
Closes: https://lore.kernel.org/linux-next/[e-mail]/
Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

arch/powerpc/crypto/aes-gcm-p10-glue.c

···
 				    void *rkey, u8 *iv, void *Xi);
 asmlinkage void aes_p10_gcm_decrypt(u8 *in, u8 *out, size_t len,
 				    void *rkey, u8 *iv, void *Xi);
-asmlinkage void gcm_init_htable(unsigned char htable[256], unsigned char Xi[16]);
+asmlinkage void gcm_init_htable(unsigned char htable[], unsigned char Xi[]);
 asmlinkage void gcm_ghash_p10(unsigned char *Xi, unsigned char *Htable,
 		unsigned char *aad, unsigned int alen);