block: Use macros from compiler.h instead of __attribute__((...))

To increase compiler portability there are several macros defined
in <linux/compiler.h> for various gcc __attribute((..)) constructs.
I've made sure gcc these specific were replaced with the right
macro and an #include <linux/compiler.h> was placed where needed.

Signed-off-by: Gideon Israel Dsouza <gidisrael@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/partitions/karma.c b/block/partitions/karma.c
index 0ea1931..9721fa5 100644
--- a/block/partitions/karma.c
+++ b/block/partitions/karma.c
@@ -8,6 +8,7 @@
 
 #include "check.h"
 #include "karma.h"
+#include <linux/compiler.h>
 
 int karma_partition(struct parsed_partitions *state)
 {
@@ -26,7 +27,7 @@
 		} d_partitions[2];
 		u8 d_blank[208];
 		__le16 d_magic;
-	} __attribute__((packed)) *label;
+	} __packed *label;
 	struct d_partition *p;
 
 	data = read_part_sector(state, 0, &sect);