gunzip: Update lenp even on error

This allows the caller to easily detect how much of the destination buffer
has been used.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/gunzip.c b/lib/gunzip.c
index 35abfb38..f469fcb 100644
--- a/lib/gunzip.c
+++ b/lib/gunzip.c
@@ -73,6 +73,7 @@
 						int stoponerr, int offset)
 {
 	z_stream s;
+	int err = 0;
 	int r;
 
 	s.zalloc = gzalloc;
@@ -92,13 +93,13 @@
 		if (stoponerr == 1 && r != Z_STREAM_END &&
 		    (s.avail_out == 0 || r != Z_BUF_ERROR)) {
 			printf("Error: inflate() returned %d\n", r);
-			inflateEnd(&s);
-			return -1;
+			err = -1;
+			break;
 		}
 		s.avail_in = *lenp - offset - (int)(s.next_out - (unsigned char*)dst);
 	} while (r == Z_BUF_ERROR);
 	*lenp = s.next_out - (unsigned char *) dst;
 	inflateEnd(&s);
 
-	return 0;
+	return err;
 }