[BUILTIN] Remove unnecessary restoration of format string in printf

Currently we try to preserve the format string which is stored in
argv after temporarily modifying it.  This is unnecessary as it's
only ever used once.  This patch gets rid of it.

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

ChangeLog

@@ -5,6 +5,7 @@
 	* Replace open-coded flushall in preadbuffer.
 	* Add likely tag in outmem.
 	* Add ifdefs around MEM_OUT handling in outmem.
+	* Remove unnecessary restoration of format string in printf.
 2014-10-13  Eric Blake <eblake@redhat.com>

src/bltin/printf.c

@@ -207,7 +207,6 @@ pc:
 				if (print_escape_str(start, param, array,
 						     getstr()))
 					goto out;
-				*fmt = 'b';
 				break;
 			case 'c': {
 				int p = getchr();