libv4l: depends on jpeg so must select it

Fixes http://autobuild.buildroot.net/results/3053854fccd65bc5b28384f2a2039a33abeeea47



The introduction of the error message for the jpeg virtual package exposes
this kind of error.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>