MLK-13547 configs: mx7ulp_evk: enable ethernet boot support

MLK-13547 configs: mx7ulp_evk: enable ethernet boot support

Since we can use USB ethernet instead of local ethernet, add ethernet support
for it. To use USB ethernet function at u-boot, just plug in Micro-AB cable
at USBOTG1 port with USB2Ethernet adapter connected.

Signed-off-by: Peter Chen <peter.chen@nxp.com>
(cherry picked from commit 60ffddf87cf6b8502c5d5fc6540364adfd66ebb3)
Signed-off-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit 63c2e1de37e1e24f35279f50efa5a330e2cb3d07)
(cherry picked from commit c82f3bef0aa0cba4937eb6c39501e446dca01746)