Bug 3330205 Put blanks and zeroes in const area

Change-Id: I8f25aebd1ded3617dc60951271767281f73b8684
diff --git a/libc/stdio/fvwrite.c b/libc/stdio/fvwrite.c
index 57a57e6..39d0604 100644
--- a/libc/stdio/fvwrite.c
+++ b/libc/stdio/fvwrite.c
@@ -48,7 +48,7 @@
 __sfvwrite(FILE *fp, struct __suio *uio)
 {
 	size_t len;
-	char *p;
+	const char *p;
 	struct __siov *iov;
 	int w, s;
 	char *nl;