ramips: fix D240 mini-PCIe power control GPIOs

ramips: fix D240 mini-PCIe power control GPIOs

In commit b11c51916cb9 ("ramips: Improve Sanlinking D240 config") I made
a mistake with regards GPIO numbering. And in addition to specifying the
wrong GPIO for controling the power of one of the mini-PCIe, I recently
discovered that the power of both slots can be controlled.

This patch specifies the correct GPIO for the left-most mini-PCIe slot
of the D240 (labeled power_mpcie2 since the slot is attached to SIM2),
and adds a GPIO that can be used to control the power of the other
mini-PCIe slot (labeled power_mpcie1).

Signed-off-by: Kristian Evensen <kristian.evensen@gmail.com>
[do not use the gpio active macros for the gpio-export value]
Signed-off-by: Mathias Kresin <dev@kresin.me>