dvb-apps: fix avr32 build failure

When building for avr32, the build fails as follows.

  cc1: error: unrecognized command line option "-Wno-packed-bitfield-compat"

An example of an autobuild failure arising from this is the following.

  http://autobuild.buildroot.net/results/92e/92e472004812a3616f62d766a9ea07a997a66e89/



Clearly, not all toolchains provide a gcc that understands
the -Wno-packed-bitfield-compat flag; remove usage of this flag.

Signed-off-by: Simon Dawson <spdawson@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>