gpio: zynq: Fix warnings in the driver

This patch fixes the below warning
	-->Block comments should align the * on each line.
	-->suspect code indent for conditional statements.
	-->Prefer 'unsigned int' to bare use of 'unsigned'

Signed-off-by: Nava kishore Manne <navam@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>