greybus: endo: move endo id map declaration to endo.h

There is a sparse warning. The endo id map is also
used in endo.c. Should define in endo.h
Signed-off-by: Phong Tran <tranmanphong@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/core.c

@@ -18,8 +18,6 @@
 
 #include "greybus.h"
 
-extern struct ida greybus_endo_id_map;
-
 /* Allow greybus to be disabled at boot if needed */
 static bool nogreybus;
 #ifdef MODULE

drivers/staging/greybus/endo.h

@@ -46,6 +46,7 @@ struct gb_endo {
 };
 #define to_gb_endo(d) container_of(d, struct gb_endo, dev)
 
+extern struct ida greybus_endo_id_map;
 
 /* Greybus "private" definitions */
 struct greybus_host_device;