Davinci: promote da8xx_pinmux_setup()

Rename da8xx_pinmux_setup() to davinci_cfg_reg_list() and promote it for use in
other SOCs that may need the ability to configure multiple pins in one shot.

Signed-off-by: Cyril Chemparathy <cyril@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>