sunxi: disable sxiuart at fdt bus

The sxiuart is basically a com(4) driver with a special
interrupt handler. As the sunxi fdtbus port is still very
rough, it makes no harm to disable sxiuart on it. The uart
driver will be replaced by an upcoming fdtcom driver.

Author: bluerise

sys/arch/armv7/conf/generic.sunxi

@@ -14,7 +14,7 @@ sxidog*		at sunxi?		# watchdog timer
 sxidog*		at fdt?			# watchdog timer
 sxirtc*		at sunxi?		# Real Time Clock
 sxiuart*	at sunxi?		# onboard UARTs
-sxiuart*	at fdt?			# onboard UARTs
+#sxiuart*	at fdt?			# onboard UARTs
 sxie*		at sunxi?
 ahci*		at sunxi?		# AHCI/SATA (shim)
 ehci*		at sunxi?		# EHCI (shim)