crypto: lib/chacha20poly1305 - Add missing function declaration

This patch adds a declaration for chacha20poly1305_selftest to
silence a sparse warning.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

lib/crypto/chacha20poly1305.c

@@ -21,8 +21,6 @@
 
 #define CHACHA_KEY_WORDS	(CHACHA_KEY_SIZE / sizeof(u32))
 
-bool __init chacha20poly1305_selftest(void);
-
 static void chacha_load_key(u32 *k, const u8 *in)
 {
 	k[0] = get_unaligned_le32(in);