kernel.h: split out instruction pointer accessors

bottom_half.h needs _THIS_IP_ to be standalone, so split that and
_RET_IP_ out from kernel.h into the new instruction_pointer.h.  kernel.h
directly needs them, so include it there and replace the include of
kernel.h with this new file in bottom_half.h.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Stephen Rothwell <[email protected]>
Signed-off-by: Andy Shevchenko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/include/linux/bottom_half.h b/include/linux/bottom_half.h
index 11d107d..fc53e0a 100644
--- a/include/linux/bottom_half.h
+++ b/include/linux/bottom_half.h
@@ -2,7 +2,7 @@
 #ifndef _LINUX_BH_H
 #define _LINUX_BH_H
 
-#include <linux/kernel.h>
+#include <linux/instruction_pointer.h>
 #include <linux/preempt.h>
 
 #if defined(CONFIG_PREEMPT_RT) || defined(CONFIG_TRACE_IRQFLAGS)