Rename __attribute__((packed)) --> __packed

Also unify __attribute__ ((..)) to __attribute__((..)) and
handle ((__packed__)) like ((packed))

Change-Id: Ie60a51c3fa92b5009724a5b7c2932e361bf3490c
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/15921
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

payloads/libpayload/include/fmap_serialized.h

@@ -56,7 +56,7 @@ struct fmap_area {
 	uint32_t size;                  /* size in bytes */
 	uint8_t  name[FMAP_STRLEN];     /* descriptive name */
 	uint16_t flags;                 /* flags for this area */
-}  __attribute__((packed));
+}  __packed;
 
 struct fmap {
 	uint8_t  signature[8];		/* "__FMAP__" (0x5F5F464D41505F5F) */
@@ -68,6 +68,6 @@ struct fmap {
 	uint16_t nareas;		/* number of areas described by
 					   fmap_areas[] below */
 	struct fmap_area areas[];
-} __attribute__((packed));
+} __packed;
 
 #endif	/* FLASHMAP_SERIALIZED_H__ */