ARM: dts: Revert disabling of smc91x for n900

ARM: dts: Revert disabling of smc91x for n900

Revert "ARM: dts: Disable smc91x on n900 until bootloader
dependency is removed". We've now fixed the issues that
caused problems with uninitialized hardware depending on
the bootloader version. Mostly things got fixed with
the following commits:

9a894953a97b ("ARM: dts: Fix bootloader version dependencies by muxing n900 smc91x pins")
7d2911c43815 ("net: smc91x: Fix gpios for device tree based booting")

Note that this only affects the early development boards
with Ethernet that we still have in a few automated boot
test systems. And it's also available supposedly in some
versions of qemu.

Tested-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Tony Lindgren <tony@atomide.com>