tcgbios: Fix a typo in the sha256 algo description

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

lib/libtpm/sha256.c

diff --git a/lib/libtpm/sha256.c b/lib/libtpm/sha256.c
index fb67e19..2a09af6 100644
--- a/lib/libtpm/sha256.c
+++ b/lib/libtpm/sha256.c
@@ -90,7 +90,7 @@
 	 *
 	 *  0 <= i <= 15:
 	 *    W(t) = M(t)
-	 * 16 <= i <= 79:
+	 * 16 <= i <= 63:
 	 *    W(t) = sigma1(W(t-2)) + W(t-7) + sigma0(W(t-15)) + W(t-16)
 	 */