lcd: dt: extract simplefb support

lcd: dt: extract simplefb support

We now have api functions that can support compiling simplefb code as its own
module. Since this code is not part of the display functionality, extract it
to its own file.

Raspberry Pi is updated to accommodate the changes.

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