staging: sm7xxfb: change return of sm7xx_vga_setup

change return type of sm7xx_vga_setup() to void as we are not using
the return type anywhere. if this function fails we fall back to the
default configuration.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>