ENGR00262502-2 [MX6Q/MX6DLS]Add commandline option to route enet irq to gpio

ENGR00262502-2 [MX6Q/MX6DLS]Add commandline option to route enet irq to gpio

Add a command line option to route the ENET interrupts to the GPIO_1_6.
To route the ENET interrupts to GPIO_6 add "enet_gpio_6" to the
kernel command line.

Also remove the CONFIG option (MX6_ENET_IRQ_TO_GPIO).

This commit should be applied on top of following commits:
72c86f0b9a953e91bb1ed31021b71f337050bc28
808863866d2c17aeb3e70a7fcd094bd96db4b601
bae4d40849f3acdd9663f5a0857c9415ed7e6d5d

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