Fix bitmap display for atmel lcd controller

The current lcd_display_bitmap() function does not work properly
for the Atmel LCD controller.

2 fixes need to be done:-

(a) when setting the colour map, use the lcd_setcolreg() function
    as provided by the Atmel driver
(b) the data is never actually written to the lcd framebuffer !!

Signed-off-by: Mark Jackson <mpfj@mimc.co.uk>