arch/microblaze/include/asm/entry.h: Include "linux/linkage.h" to avoid compiling issue

"entry.h" needs 'asmlinkage', and "asm/linkage.h" does not provide it.
So need include "linux/linkage.h" to use generic one instead of.

The related error (with allmodconfig under microblaze):

    CC [M]  drivers/net/ethernet/emulex/benet/be_main.o
  In file included from ./arch/microblaze/include/asm/processor.h:17:0,
                   from include/linux/prefetch.h:14,
                   from drivers/net/ethernet/emulex/benet/be_main.c:18:
  ./arch/microblaze/include/asm/entry.h:33:19: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void'
   extern asmlinkage void do_notify_resume(struct pt_regs *regs, int in_syscall);
                     ^

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/include/asm/entry.h

@@ -15,6 +15,7 @@
 
 #include <asm/percpu.h>
 #include <asm/ptrace.h>
+#include <linux/linkage.h>
 
 /*
  * These are per-cpu variables required in entry.S, among other