[XTENSA] Remove non-rt signal handling

The non-rt signal handling was never really used, so we don't break
anything. This patch also cleans up the signal stack-frame to make
it independent from the processor configuration. It also improves
the method used for controlling single-stepping. We now save and
restore the 'icountlevel' register that controls single stepping
and set or clear the saved state to enable or disable it.

Signed-off-by: Chris Zankel <chris@zankel.net>
diff --git a/include/asm-xtensa/ptrace.h b/include/asm-xtensa/ptrace.h
index cad83e8..77ff02d 100644
--- a/include/asm-xtensa/ptrace.h
+++ b/include/asm-xtensa/ptrace.h
@@ -99,7 +99,8 @@
 	unsigned long windowbase;	/*  48 */
 	unsigned long windowstart;	/*  52 */
 	unsigned long syscall;		/*  56 */
-	int reserved[2];		/*  64 */
+	unsigned long icountlevel;	/*  60 */
+	int reserved[1];		/*  64 */
 
 	/* Make sure the areg field is 16 bytes aligned. */
 	int align[0] __attribute__ ((aligned(16)));