Add disabled SPIFC controller node with instruction on how to enable
it while lowering capabilities of the eMMC controller from 8bits bus
width to 4bits bus width, it's data pins 4 to 7 being shared with
the SPI NOR controller pins.
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20200313090713.15147-5-narmstrong@baylibre.com