MIPS: Loongson: Do not register 8250 platform device from module.

If CONFIG_SERIAL_8250 is set to m, the Loongson seria.ko module might get
unloaded while the serial driver 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>
Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Patchwork: https://patchwork.linux-mips.org/patch/10538/

arch/mips/loongson/common/Makefile

@@ -3,15 +3,13 @@
 #
 
 obj-y += setup.o init.o cmdline.o env.o time.o reset.o irq.o \
-    bonito-irq.o mem.o machtype.o platform.o
+    bonito-irq.o mem.o machtype.o platform.o serial.o
 obj-$(CONFIG_PCI) += pci.o
 
 #
 # Serial port support
 #
 obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
-loongson-serial-$(CONFIG_SERIAL_8250) := serial.o
-obj-y += $(loongson-serial-m) $(loongson-serial-y)
 obj-$(CONFIG_LOONGSON_UART_BASE) += uart_base.o
 obj-$(CONFIG_LOONGSON_MC146818) += rtc.o