drivers: net: fsl-mc: Link MC boot to PHY_RESET_R

drivers: net: fsl-mc: Link MC boot to PHY_RESET_R

DPAA2 platforms boot the Management Complex based on the u-boot env
variable "mcinitcmd". Instead of doing this step on each platform
individually, define a single mc_env_boot function in the MC driver,
since it's semantically tied to it.

Call the function in a per-board reset_phy hook, as it gets called at a
later moment, when all board PHY devices have been initialized.

Signed-off-by: Bogdan Purcareata <bogdan.purcareata@nxp.com>
Signed-off-by: Heinz Wrobel <heinz.wrobel@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>