ENGR00256893-2 MX6Q/DL-Fix Ethernet performance issue when WAIT mode is active

ENGR00256893-2 MX6Q/DL-Fix Ethernet performance issue when WAIT mode is active

All of the interrupts from the ENET block are not routed to
the GPC block. Hence ENET interrupts are not able to wake
up the SOC when the system is in WAIT mode. And the ENET
interrupt gets serviced only when another interrupt causes
the SOC to exit WAIT mode. This impacts the ENET performance.

To fix the issue two options:
1. Route the ENET interrupt to a GPIO. Need to enable the
CONFIG_MX6_ENET_IRQ_TO_GPIO in the config.
This patch provides support for routing the ENET interrupt
to GPIO_1_6. Routing to this GPIO requires no HW board mods.
If the GPIO_1_6 is being used for some other peripheral,
this patch can be followed to route the ENET interrupt to
any other GPIO though a HW mode maybe required.
2. If the GPIO mechanism cannot be used and is not enabled
by the above mentioned config, the patch will disable entry
to WAIT mode until ENET clock is active. When the ENET clock
is disabled, WAIT mode will be automatically enetered.

Signed-off-by: Ranjani Vaidyanathan <ra5478@freescale.com>