MN10300: Introduce a general config option for kernel debugger hooks

Introduce a general config option for kernel debugger hooks so that both
gdbstub and kgdb can use it and add a header file for both debuggers to use.

Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/arch/mn10300/Kconfig b/arch/mn10300/Kconfig
index 10971be..25e6a0b 100644
--- a/arch/mn10300/Kconfig
+++ b/arch/mn10300/Kconfig
@@ -403,7 +403,7 @@
 
 config GDBSTUB_IRQ_LEVEL
 	int "GDBSTUB interrupt priority"
-	depends on GDBSTUB
+	depends on KERNEL_DEBUGGER
 	range 0 1 if LINUX_CLI_LEVEL = 2
 	range 0 2 if LINUX_CLI_LEVEL = 3
 	range 0 3 if LINUX_CLI_LEVEL = 4