common/lcd.c: cleanup use of global variables

common/lcd.c: cleanup use of global variables

lcd_color_fg and lcd_color_bg had to be declared in board specific
code, but were not actually used there; in addition, we have getter /
setter functions for these, which were not used either.

Get rid of the global variables, and use the getter function where
needed (so far no setter calls are needed).

Signed-off-by: Wolfgang Denk <[email protected]>
Cc: Alessandro Rubini <[email protected]>
Cc: Anatolij Gustschin <[email protected]>
Cc: Bo Shen <[email protected]>
Cc: Haavard Skinnemoen <[email protected]>
Cc: Kyungmin Park <[email protected]>
Cc: Marek Vasut <[email protected]>
Cc: Minkyu Kang <[email protected]>
Cc: Nikita Kiryanov <[email protected]>
Cc: Simon Glass <[email protected]>
Cc: Stelian Pop <[email protected]>
Cc: Tom Warren <[email protected]>
Acked-by: Simon Glass <[email protected]>
Acked-by: Jeroen Hofstee <[email protected]>
[agust: also fixed cm_t35 board while rebasing]
Signed-off-by: Anatolij Gustschin <[email protected]>