kernel: use macros from compiler.h instead of __attribute__((...))

To increase compiler portability there is <linux/compiler.h> which
provides convenience macros for various gcc constructs.  Eg: __weak for
__attribute__((weak)).  I've replaced all instances of gcc attributes
with the right macro in the kernel subsystem.

Signed-off-by: Gideon Israel Dsouza <gidisrael@gmail.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kexec.c

@@ -32,6 +32,7 @@
 #include <linux/vmalloc.h>
 #include <linux/swap.h>
 #include <linux/syscore_ops.h>
+#include <linux/compiler.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
@@ -1551,10 +1552,10 @@ void vmcoreinfo_append_str(const char *fmt, ...)
  * provide an empty default implementation here -- architecture
  * code may override this
  */
-void __attribute__ ((weak)) arch_crash_save_vmcoreinfo(void)
+void __weak arch_crash_save_vmcoreinfo(void)
 {}
 
-unsigned long __attribute__ ((weak)) paddr_vmcoreinfo_note(void)
+unsigned long __weak paddr_vmcoreinfo_note(void)
 {
 	return __pa((unsigned long)(char *)&vmcoreinfo_note);
 }