btrfs-progs: Stop stomping on 'name' input parameter

In btrfs_name_hash, Local variable 'buf' is declared as

	__u32 buf[2];

but we then try to do this:

	buf[0] = 0x67452301;
	buf[1] = 0xefcdab89;
	buf[2] = 0x98badcfe;
	buf[3] = 0x10325476;

Oops. Fix buf to be the proper size.
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/hash.c

@@ -81,7 +81,7 @@ u64 btrfs_name_hash(const char *name, int len)
 	__u32	hash;
 	__u32	minor_hash = 0;
 	const char	*p;
-	__u32		in[8], buf[2];
+	__u32		in[8], buf[4];
 	u64		hash_result;
 
 	if (len == 1 && *name == '.') {