staging: fbtft: Prefer using the BIT macro

Replacing all occurrences of (1<<x) with BIT(x) to fix checkpatch issue.
CHECK:Prefer using the BIT macro

Signed-off-by: Mamta Shukla <mamtashukla555@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>