bcm2708: Add support for MAX7301 over SPI

Signed-off-by: Franz Pletz <fpletz@fnordicwalking.de>
bcm2708: Increase ARCH_NR_GPIOS and fix bcm2708_gpio

Signed-off-by: Franz Pletz <fpletz@fnordicwalking.de>
gpio-max7301: bcm2708_gpio only supports 8 bits_per_word

Signed-off-by: Franz Pletz <fpletz@fnordicwalking.de>