The splash screen loading code can be reused by other compulab boards.
For now extract it to a common location for further reuse.

This also switches the splash code dependency from CONFIG_LCD to
CONFIG_SPLASH_SCREEN as it should normally be.

In addition this patch fixes the accidental dependency of the
get_board_mem_timings() function on CONFIG_LCD, by just moving the
splash code and leaving the above function intact.

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
Reviewed-by: Tom Rini <trini@ti.com>