gpio: omap: handle pin config bias flags

gpio: omap: handle pin config bias flags

Modify omap_gpio_set_config() to handle pin config bias flags by calling
gpiochip_generic_config().

The pin group for the gpio line must have the corresponding pinconf
properties:

PIN_CONFIG_BIAS_PULL_UP requires "pinctrl-single,bias-pullup"
PIN_CONFIG_BIAS_PULL_DOWN requires "pinctrl-single,bias-pulldown"

This is necessary for pcs_pinconf_set() to find the requested bias
parameter in the PIN_MAP_TYPE_CONFIGS_GROUP pinctrl map.

Signed-off-by: Drew Fustini <drew@beagleboard.org>
Acked-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20200715213738.1640030-1-drew@beagleboard.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>