kgdb: Remove unused DCPU_SSTEP definition

From doing a 'git log --patch kernel/debug', it looks as if DCPU_SSTEP
has never been used.  Presumably it used to be used back when kgdb was
out of tree and nobody thought to delete the definition when the usage
went away.  Delete.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>

kernel/debug/debug_core.h

@@ -33,7 +33,6 @@ struct kgdb_state {
 #define DCPU_WANT_MASTER 0x1 /* Waiting to become a master kgdb cpu */
 #define DCPU_NEXT_MASTER 0x2 /* Transition from one master cpu to another */
 #define DCPU_IS_SLAVE    0x4 /* Slave cpu enter exception */
-#define DCPU_SSTEP       0x8 /* CPU is single stepping */
 
 struct debuggerinfo_struct {
 	void			*debuggerinfo;