kgdb,powerpc: Replace hardcoded offset by BREAK_INSTR_SIZE

kgdb_handle_breakpoint checks the first arch_kgdb_breakpoint
which is not known by gdb that's why is necessary jump over
it. The jump lenght is equal to BREAK_INSTR_SIZE that's
why is cleaner to use defined macro instead of hardcoded
non-described offset.

Signed-off-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index 82a7b22..7f61a3a 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -129,7 +129,7 @@
 		return 0;
 
 	if (*(u32 *) (regs->nip) == *(u32 *) (&arch_kgdb_ops.gdb_bpt_instr))
-		regs->nip += 4;
+		regs->nip += BREAK_INSTR_SIZE;
 
 	return 1;
 }