staging: sm750fb: replace lynx_crtc methods with function calls

The methods in lynx_crtc always use the same implementation and there is
no point to use redirection rather than direct function call.

Signed-off-by: Mike Rapoport <mike.rapoport@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>