minidlna, libsvg: do not use libjpeg directly, use jpeg

libjpeg should not be selected directly, as it is one implementation
of the virtual jpeg package. Consequently, this commit moves minidlna
and libsvg to use the jpeg virtual package instead.

The build has been tested with both libjpeg and jpeg-turbo variants.

Fixes:

  http://autobuild.buildroot.org/results/a12/a12760dea9e9d7ca62d14d0821539cc4b0c76835/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>