phy: zynqmp: Move assert/de-assert to a separate functions

phy: zynqmp: Move assert/de-assert to a separate functions

Currently assert/de-assert are controlled through reset-controller
framework. Since these functions are non-blocking calls, changed the
code to wait until the assert/de-assert is done by the reset framework.
Waiting is done by reading the status from the reset-controller
framework.

Signed-off-by: Anurag Kumar Vulisha <anuragku@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>