wimax/i2400m: add missing debug submodule definition

The i2400m driver was missing the definition for the sysfs debug
level, which is declared in debug-levels.h.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
diff --git a/drivers/net/wimax/i2400m/driver.c b/drivers/net/wimax/i2400m/driver.c
index 20d574c..7ba00de 100644
--- a/drivers/net/wimax/i2400m/driver.c
+++ b/drivers/net/wimax/i2400m/driver.c
@@ -785,6 +785,7 @@
 	D_SUBMODULE_DEFINE(netdev),
 	D_SUBMODULE_DEFINE(rfkill),
 	D_SUBMODULE_DEFINE(rx),
+	D_SUBMODULE_DEFINE(sysfs),
 	D_SUBMODULE_DEFINE(tx),
 };
 size_t D_LEVEL_SIZE = ARRAY_SIZE(D_LEVEL);