x86: Probe pinctrl driver in cpu_init_r()

At present pinctrl driver gets probed in ich6_gpio driver's probe
routine, which has two issues:

 - Pin's PADs only gets configured when GPIO driver is probed, which
   is not done by default. This leaves the board in a partially
   functional state as we must initialize PADs correctly to get
   perepherals fully working.
 - The probe routine of pinctrl driver is called multiple times, as
   normally there are multiple GPIO controllers. It should really
   be called just once.

Move the call to syscon_get_by_driver_data() from ich6_gpio driver
to cpu_init_r().

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: George McCollister <george.mccollister@gmail.com>
Tested-by: George McCollister <george.mccollister@gmail.com>