crypto: wp512 - disable kmsan checks in wp512_process_buffer()

The memory sanitizer causes excessive register spills in this function:

crypto/wp512.c:782:13: error: stack frame size (2104) exceeds limit (2048) in 'wp512_process_buffer' [-Werror,-Wframe-larger-than]

Assume that this one is safe, and mark it as needing no checks to
get the stack usage back down to the normal level.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>