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We may need gpio pull mode later, so add this function.
Besides fix a set pull mode bug, and save gpio clock gate,
when operate the gpio, we will enable gpio clock, when
finish gpio operate, restore gpio clock gate status.

Change-Id: Ia1d602804f571a17f5ddc499908663b968b02974

There are 5 groups of GPIO (GPIO0~GPIO4), totally have 122 GPIOs
on rk3399 platform.
The pull direction(pullup or pulldown) for all of GPIOs are
software-programmable.
At the moment, we add the gpio basic driver since reset or power off
the devices from gpio configuration for BL31.