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>

src/lib/timestamp.c

@@ -16,6 +16,7 @@
 #include <assert.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <compiler.h>
 #include <console/console.h>
 #include <cbmem.h>
 #include <symbols.h>
@@ -30,7 +31,7 @@
 /* When changing this number, adjust TIMESTAMP() size ASSERT() in memlayout.h */
 #define MAX_BSS_TIMESTAMP_CACHE 16
 
-struct __attribute__((__packed__)) timestamp_cache {
+struct __packed timestamp_cache {
 	uint32_t cache_state;
 	struct timestamp_table table;
 	/* The struct timestamp_table has a 0 length array as its last field.