Kconfig: atben framework "driver" can't be a module

... because spi_register_board_info isn't exported. Also change the
description from "driver" to "framework".
atben.c: use spi-jz4740-gpio also if compiled as module
atben.c: don't make MMC pin configuration optional (it's simpler this way)

Nobody is bothered if we configure the pins in atben_reset and it makes
it easier to make sure they are configured when necessary.
spi-jz4740-gpio.c (spi_jz4740_gpio_remove): don't forget to free GPIOs