gpt_partition: Mark grub_gpt_partentry as having natural alignment

gpt_partition contains grub_guid. We need to decide whether the whole
structure is unaligned and then we need to use packed_guid. But we never
have unaligned part entries as we read them in an aligned buffer from disk.
Hence just make it all aligned.

Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>

include/grub/gpt_partition.h

@@ -67,7 +67,7 @@ struct grub_gpt_partentry
   grub_uint64_t end;
   grub_uint64_t attrib;
   char name[72];
-} GRUB_PACKED;
+};
 
 grub_err_t
 grub_gpt_partition_map_iterate (grub_disk_t disk,