lcd: introduce lcd_set_cmap

lcd: introduce lcd_set_cmap

Reduce the lcd_display_bitmap #ifdef complexity by extracting Atmel-specific
code for setting cmap for bitmap images into a new function lcd_set_cmap().
A default version is implemented with the remainder of the code.

Signed-off-by: Nikita Kiryanov <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Tested-by: Bo Shen <[email protected]>
Tested-by: Josh Wu <[email protected]>
Cc: Bo Shen <[email protected]>
Cc: Simon Glass <[email protected]>
Cc: Anatolij Gustschin <[email protected]>