pinctrl: samsung: Decouple direction setting from pinctrl

This patch makes the pinctrl-samsung driver configure GPIO direction on
its own, without using the pinctrl_gpio_direction_*() "helpers". The
rationale behind this change is as follows:
 - pinctrl-samsung does not need translation from GPIO namespace to
   pinctrl namespace to handle GPIO operations - GPIO chip and offset
   therein are enough to calculate necessary offsets and bit masks in
   constant time,
 - the pinctrl_gpio_direction_*() functions do not do anything useful
   other than translating the pin into pinctrl namespace and calling the
   .gpio_set_direction() from pinmux_ops of the controller,
 - the undesirable side effect of using those helpers is losing the
   ability to change GPIO direction in atomic context, because they
   explicitly use a mutex for synchronization,

Results of this patch are:
 - fixed warnings about scheduling while atomic in code that needs to
   set GPIO direction in atomic context (e.g. interrupt handler),
 - reduced overhead of bitbanging drivers that use gpio_direction_*(),
   e.g. i2c-gpio.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>