common/lcd: fix build breakage for at91sam9x5ek and trats boards

Commit 203c37b8
(common lcd: simplify core functions)

and commit bfdcc65e
(common lcd: simplify lcd_display_bitmap)

caused build breakage for at91sam9x5ek board configurations
and for trats board. Fix these build errors.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Acked-by: Nikita Kiryanov <nikita@compulab.co.il>