Shush some dead assignments.

Appease clang scan-build a bit. I'm not sure it's actually worth silencing all
of them because some of them look like preserving invariants between local
variables, but some are clearly pointless or can be restructured slightly.

Change-Id: I0bc81e2589bb402ff3ef0182d7a8921e31b85052
Reviewed-on: https://boringssl-review.googlesource.com/2205
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/asn1/tasn_dec.c b/crypto/asn1/tasn_dec.c
index 80c8b7d..69bacec 100644
--- a/crypto/asn1/tasn_dec.c
+++ b/crypto/asn1/tasn_dec.c
@@ -599,14 +599,13 @@
 	{
 	int flags, aclass;
 	int ret;
-	const unsigned char *p, *q;
+	const unsigned char *p;
 	if (!val)
 		return 0;
 	flags = tt->flags;
 	aclass = flags & ASN1_TFLG_TAG_CLASS;
 
 	p = *in;
-	q = p;
 
 	if (flags & ASN1_TFLG_SK_MASK)
 		{
@@ -663,7 +662,7 @@
 		while(len > 0)
 			{
 			ASN1_VALUE *skfield;
-			q = p;
+			const unsigned char *q = p;
 			/* See if EOC found */
 			if (asn1_check_eoc(&p, len))
 				{