openrisc: use kbuild.h instead of defining macros in asm-offset.c

This is modelled on commits such as the one below:

Commit fc1c3a00 ("sh: use kbuild.h
instead of defining macros in asm-offsets.c") introduced in v2.6.26.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Jonas Bonn <jonas@southpole.se>

arch/openrisc/kernel/asm-offsets.c

@@ -34,15 +34,11 @@
 #include <linux/mm.h>
 #include <linux/io.h>
 #include <linux/thread_info.h>
+#include <linux/kbuild.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
 #include <asm/processor.h>
 
-#define DEFINE(sym, val) \
-		asm volatile("\n->" #sym " %0 " #val : : "i" (val))
-
-#define BLANK() asm volatile("\n->" : : )
-
 int main(void)
 {
 	/* offsets into the task_struct */