media: cxusb, dib0700: ignore XC2028_I2C_FLUSH

media: cxusb, dib0700: ignore XC2028_I2C_FLUSH

BugLink: http://bugs.launchpad.net/bugs/1751064
commit 9893b905e743ded332575ca04486bd586c0772f7 upstream.

The XC2028_I2C_FLUSH only needs to be implemented on a few
devices. Others can safely ignore it.

That prevents filling the dmesg with lots of messages like:

	dib0700: stk7700ph_xc3028_callback: unknown command 2, arg 0

Fixes: 4d37ece757a8 ("[media] tuner/xc2028: Add I2C flush callback")
Reported-by: Enrico Mioso <mrkiko.rs@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>