Separate building of corgi_ssp.c, and introduce a new hidden config option
CONFIG_CORGI_SSP_DEPRECATED for this. Aslo mark corgi_ts.c and corgi_bl.c
as deprecated.

This unbreaks the legacy configs in {corgi,spitz}_defconfig, however, SPI
based ADS7846 touchscreen driver and a new SPI-based corgi_lcd.c driver
with integrated backlight support are recommended.
Signed-off-by: Eric Miao <eric.miao@marvell.com>