gpio: zynq: Fix problem with unbalanced pm_runtime_enable

Add missing pm_runtime_disabled to remove().

Error log:
root@zynqmp:~# modprobe gpio_zynq
root@zynqmp:~# lsmod
    Not tainted
gpio_zynq 7086 0 - Live 0xffffffbffc00a000
root@zynqmp:~# rmmod gpio_zynq
root@zynqmp:~# lsmod
    Not tainted
root@zynqmp:~# modprobe gpio_zynq
[  246.924438] zynq-gpio ff0a0000.gpio: Unbalanced pm_runtime_enable!
root@zynqmp:~# rmmod gpio_zynq
root@zynqmp:~# lsmod
    Not tainted

Signed-off-by: Michal Simek <michal.simek@xilinx.com>