arm64: zynqmp: Remove low level UART setting cont

arm64: zynqmp: Remove low level UART setting cont

There is no reason to do serial initialization. Uart driver does it already
based on DT. Good effect is that it is clear which interface is console.
The same change was done in past by commit 84d2bbf082fa ("arm64: zynqmp:
Remove low level UART setting").

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/91a73f292bafc4b64ed09954cc23780496da4b65.1648125082.git.michal.simek@xilinx.com