Remove superflous comment

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/tf-psa-crypto/drivers/builtin/src/des.c b/tf-psa-crypto/drivers/builtin/src/des.c
index 73afb04..4bb354a 100644
--- a/tf-psa-crypto/drivers/builtin/src/des.c
+++ b/tf-psa-crypto/drivers/builtin/src/des.c
@@ -389,9 +389,6 @@
     return 0;
 }
 
-/*
- * Internal function for key expansion.
- */
 static void mbedtls_des_setkey(uint32_t SK[32], const unsigned char key[MBEDTLS_DES_KEY_SIZE])
 {
     int i;