Adds pinctrl driver for Broadcom Capri (BCM281xx) SoCs.

v4: - PINCTRL selected in Kconfig, PINCTRL_CAPRI selected in bcm_defconfig
    - make use of regmap
    - change CAPRI_PIN_UPDATE from macro to inline function.
    - Handle pull-up strength arg in Ohm instead of enum
v3: Re-work driver to be based on generic pin config. Moved config selection
    from Kconfig to bcm_defconfig.
v2: Use hyphens instead of underscore in DT property names.
Signed-off-by: Sherman Yin <syin@broadcom.com>
Reviewed-by: Christian Daudt <bcm@fixthebug.org>
Reviewed-by: Matt Porter <matt.porter@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>