package/tvheadend: re-enable package on microblaze

package/tvheadend: re-enable package on microblaze

Package tvheadend has been disabled on microblaze with this commit:
https://git.buildroot.net/buildroot/commit/?id=e1a59357e4dfe8fe9c9119d4b2bc9e4ec36eb3d0
but commit log says that build failure is due to "some assertion
failure in binutils", that is true. But those assertion failures in
binutils are caused by package's Makefile itself that has been fixed by
previous patch. So re-enable package for microblaze.

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>