Update bcm_defconfig with new pinctrl CONFIG

To be consistent with other Broadcom drivers, the Broadcom Capri pinctrl
driver and its related CONFIG option are renamed to bcm281xx.

This commit updates the defconfig that enables the pinctrl driver.

Signed-off-by: Sherman Yin <syin@broadcom.com>
Reviewed-by: Matt Porter <mporter@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>