staging: dgnc: delete all references to 'flipbuf'

This patch deletes all references to 'flipbuf'.Memory is allocated and
freed but never used anywhere in the driver.Also deleted an ununsed
Macro defined in the header file.

Signed-off-by: Gujulan Elango Hari Prasath <hgujulan@visteon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>