net: zynq: Add support for GEM reset

Perform reset before core initialization.
Standard flow which close to 99% users are using getting all IPs out of
reset that there is no need to reset IP again. This is because of all low
level initialization is done in previous bootloader stage.
In SOM case these IPs are not touched by previous bootloader stage that's
why reset needs to be called before IP is accessed to make sure that it is
in correct state.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
Link: https://lore.kernel.org/r/5ae1c85b282d632bb62030f1f24a0065661b9153.1638804318.git.michal.simek@xilinx.com