crypto: lib/chacha - add array bounds to function prototypes

Add explicit array bounds to the function prototypes for the parameters
that didn't already get handled by the conversion to use chacha_state:

- chacha_block_*():
  Change 'u8 *out' or 'u8 *stream' to u8 out[CHACHA_BLOCK_SIZE].

- hchacha_block_*():
  Change 'u32 *out' or 'u32 *stream' to u32 out[HCHACHA_OUT_WORDS].

- chacha_init():
  Change 'const u32 *key' to 'const u32 key[CHACHA_KEY_WORDS]'.
  Change 'const u8 *iv' to 'const u8 iv[CHACHA_IV_SIZE]'.

No functional changes.  This just makes it clear when fixed-size arrays
are expected.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>