pinctrl: zynq: use module_platform_driver to simplify the code

module_platform_driver() makes the code simpler by eliminating
boilerplate code.

Signed-off-by: Srinivas Neeli <srinivas.neeli@xilinx.com>
Link: https://lore.kernel.org/r/20220224043605.26157-1-srinivas.neeli@xilinx.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>