1. Add "drv_eth.c" for all imxrt platforms.
2. Add ksz8081 phy driver for imxrt1052-nxp-evk board.
3. Disable the LED demo in main.c file if enable the ENET
   and ksz8081 phy, because the PINs of LED and ksz8081
   reset are from the same GPIO.
4. Update the relevant Kconfig and Sconscript files.
Signed-off-by: NGavin Liu <gavin-liugang@outlook.com>