xfs: remove __arch_pack

Instead we always declare struct xfs_dir2_sf_hdr as packed.  That's
the expected layout, and while most major architectures do the packing
by default the new structure size and offset checker showed that not
only the ARM old ABI got this wrong, but various minor embedded
architectures did as well.

[Verified that no code change on x86-64 results from this change]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_da_format.h

@@ -229,7 +229,7 @@ typedef struct xfs_dir2_sf_hdr {
 	__uint8_t		count;		/* count of entries */
 	__uint8_t		i8count;	/* count of 8-byte inode #s */
 	__uint8_t		parent[8];	/* parent dir inode number */
-} __arch_pack xfs_dir2_sf_hdr_t;
+} __packed xfs_dir2_sf_hdr_t;
 
 typedef struct xfs_dir2_sf_entry {
 	__u8			namelen;	/* actual name length */

fs/xfs/xfs_linux.h

@@ -328,13 +328,6 @@ static inline __uint64_t howmany_64(__uint64_t x, __uint32_t y)
 	return x;
 }
 
-/* ARM old ABI has some weird alignment/padding */
-#if defined(__arm__) && !defined(__ARM_EABI__)
-#define __arch_pack __attribute__((packed))
-#else
-#define __arch_pack
-#endif
-
 #define ASSERT_ALWAYS(expr)	\
 	(unlikely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))