crypto: rmd160 - fix Kconfig "its" grammar

Use the possessive "its" instead of the contraction "it's"
where appropriate.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-crypto@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/Kconfig

@@ -889,7 +889,7 @@ config CRYPTO_RMD160
 
 	  RIPEMD-160 is a 160-bit cryptographic hash function. It is intended
 	  to be used as a secure replacement for the 128-bit hash functions
-	  MD4, MD5 and it's predecessor RIPEMD
+	  MD4, MD5 and its predecessor RIPEMD
 	  (not to be confused with RIPEMD-128).
 
 	  It's speed is comparable to SHA1 and there are no known attacks