i.mx: fec-uio driver

This patch adds the userspace support. In the new mode, basic
hardware initialization is performed in kernel via userspace
input/output, while the majority of code is written in the
userspace.

Signed-off-by: Sachin Saxena <sachin.saxena@nxp.com>
Signed-off-by: Apeksha Gupta <apeksha.gupta@nxp.com>
Reviewed-by: Sachin Saxena <sachin.saxena@nxp.com>