staging: sm750fb: remove unneeded switch statement

The lynxfb_ops_check_var function has two switch statements, the first
one checks for validity of var->bits_per_pixel and it is is immediatly
followed by another one that sets parameters according to
var->bits_per_pixel value. These switch statements can be merged into
one.

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