tools: Adopt __packed from kernel sources

To have a more compact way to ask the compiler to not insert alignment
paddings in a struct, making tools/ look more like kernel source code.

Cc: Adrian Hunter <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/include/linux/compiler-gcc.h

···
 
 #define  noinline	__attribute__((noinline))
 
+#define __packed	__attribute__((packed))
+
 #define __noreturn	__attribute__((noreturn))
 
 #define __printf(a, b)	__attribute__((format(printf, a, b)))

tools/perf/util/genelf_debug.c

···
  * @remark Copyright 2007 OProfile authors
  * @author Philippe Elie
  */
+#include <linux/compiler.h>
 #include <sys/types.h>
 #include <stdio.h>
 #include <getopt.h>
···
 	 * and filesize, last entry is followed by en empty string.
 	 */
 	/* follow the first program statement */
-} __attribute__((packed));
+} __packed;
 
 /* DWARF 2 spec talk only about one possible compilation unit header while
  * binutils can handle two flavours of dwarf 2, 32 and 64 bits, this is not
···
 	uhalf version;
 	uword debug_abbrev_offset;
 	ubyte pointer_size;
-} __attribute__((packed));
+} __packed;
 
 #define DW_LNS_num_opcode (DW_LNS_set_isa + 1)