xdriver_xf86-video-i740: remove package

This X.org driver has been removed from upstream X.org releases and is
related to a very specific type of hardware that isn't likely to be used
in a Buildroot context.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>