MIPS: Cobalt: Do not build MTD platform device registration code as module.

If CONFIG_MTD_PHYSMAP is set to m, the Cobalt mtd.ko module might get
unloaded while the drivers/mtd modules are still loaded resulting in
stale references to the destroyed platform_device instance.

Anyway, platform devices should always be registered indicated what
devices are present, _not_ what drivers have been configured.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/cobalt/Makefile

@@ -2,7 +2,6 @@
 # Makefile for the Cobalt micro systems family specific parts of the kernel
 #
 
-obj-y := buttons.o irq.o lcd.o led.o reset.o rtc.o serial.o setup.o time.o
+obj-y := buttons.o irq.o lcd.o led.o mtd.o reset.o rtc.o serial.o setup.o time.o
 
 obj-$(CONFIG_PCI)		+= pci.o
-obj-$(CONFIG_MTD_PHYSMAP)	+= mtd.o