serial-uartlite: Use allocated structure instead of static ones

Remove the use of the static uartlite structure.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/1573555271-2579-2-git-send-email-shubhrajyoti.datta@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>