pinctrl: zynqmp: some code cleanups

Some minor code cleanups and updates which includes
- Mention module name under help in Kconfig.
- Remove extra lines and duplicate Pin range checks.
- Replace 'return ret' with 'return 0' in success path.
- Copyright year update.
- use devm_pinctrl_register() instead pinctrl_register() in probe.

Signed-off-by: Sai Krishna Potthuri <lakshmi.sai.krishna.potthuri@xilinx.com>
Link: https://lore.kernel.org/r/1624273214-66849-1-git-send-email-lakshmi.sai.krishna.potthuri@xilinx.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>