arm: fix implicit #include <linux/init.h> in entry asm.

They use the "_INIT" macro and friends, and hence need to
source this header file, vs. relying on getting it implicitly.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

arch/arm/kernel/entry-armv.S

@@ -15,6 +15,8 @@
  *  that causes it to save wrong values...  Be aware!
  */
 
+#include <linux/init.h>
+
 #include <asm/assembler.h>
 #include <asm/memory.h>
 #include <asm/glue-df.h>