btrfs-progs: include <sys/xattr.h> instead of <attr/xattr.h>

The `btrfs` and `mkfs.btrfs` binaries are not linked against libattr
so the correct header to include is <sys/xattr.h>.

This fixes the build when attr header files are not installed.

Signed-off-by: Christophe Vu-Brugier <cvubrugier@yahoo.fr>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

cmds-restore.c

@@ -34,7 +34,7 @@
 #include <regex.h>
 #include <getopt.h>
 #include <sys/types.h>
-#include <attr/xattr.h>
+#include <sys/xattr.h>
 
 #include "ctree.h"
 #include "disk-io.h"

mkfs.c

@@ -34,7 +34,7 @@
 #include <getopt.h>
 #include <uuid/uuid.h>
 #include <ctype.h>
-#include <attr/xattr.h>
+#include <sys/xattr.h>
 #include <blkid/blkid.h>
 #include <ftw.h>
 #include "ctree.h"