drivers: video: tidss: Makefile: Add condition to compile TIDSS at SPL

To enable TIDSS driver only at SPL stage add rule to compile the TIDSS
video driver.

CONFIG_$(SPL_)VIDEO_TIDSS will compile tidss_drv, at SPL only if
CONFIG_SPL_VIDEO_TIDSS is defined and at u-boot proper if
CONFIG_VIDEO_TIDSS is defined.

Signed-off-by: Nikhil M Jain <n-jain1@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>