ARM: dts: imx: pinfunc: add MX6QDL_PAD_GPIO_6__ENET_IRQ

From "Chip Errata for the i.MX 6Dual/6Quad"

ERR006687 ENET: Only the ENET wake-up interrupt request can wake the
system from Wait mode.

The ENET block generates many interrupts. Only one of these interrupt lines
is connected to the General Power Controller (GPC) block, but a logical OR
of all of the ENET interrupts is connected to the General Interrupt Controller
(GIC). When the system enters Wait mode, a normal RX Done or TX Done does not
wake up the system because the GPC cannot see this interrupt. This impacts
performance of the ENET block because its interrupts are serviced only when
the chip exits Wait mode due to an interrupt from some other wake-up source.

Adding MX6QDL_PAD_GPIO_6__ENET_IRQ is the 1st step to
workaround this problem.

The input reg is set to 0x3c to set IOMUX_OBSRV_MUX1 to ENET_IRQ.
The mux reg value is 0x11, so that the observable mux is routed to
this pin and to the gpio controller(sion bit). These magic values
come from Ranjani Vaidyanathan's patch:
"ENGR00257847-1 MX6Q/DL-Fix Ethernet performance issue when WAIT mode is active"

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
CC: Ranjani Vaidyanathan <ra5478@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>