net: can: use kbuild magic to inherit debug settings

No need to manually copy debug settings into subdir Makefiles. kbuild
has a mechanism for inheriting, so let's use it.

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/sja1000/Makefile

@@ -12,5 +12,3 @@ obj-$(CONFIG_CAN_PEAK_PCMCIA) += peak_pcmcia.o
 obj-$(CONFIG_CAN_PEAK_PCI) += peak_pci.o
 obj-$(CONFIG_CAN_PLX_PCI) += plx_pci.o
 obj-$(CONFIG_CAN_TSCAN1) += tscan1.o
-
-ccflags-$(CONFIG_CAN_DEBUG_DEVICES) := -DDEBUG