fanotify: use __aligned_u64 in fanotify userspace metadata

Currently the userspace struct exposed by fanotify uses
__attribute__((packed)) to make sure that alignment works on multiarch
platforms.  Since this causes a severe performance penalty on some
platforms we are going to switch to using explicit alignment notation on
the 64bit values so we don't have to use 'packed'
Signed-off-by: NEric Paris <eparis@redhat.com>

include/linux/fanotify.h

@@ -79,10 +79,10 @@
 struct fanotify_event_metadata {
 	__u32 event_len;
 	__u32 vers;
-	__u64 mask;
+	__aligned_u64 mask;
 	__s32 fd;
 	__s32 pid;
-} __attribute__ ((packed));
+};
 
 struct fanotify_response {
 	__s32 fd;