tv: Allow tarval_get_bit() for tarvals with any data mode.
tv: Allow tarval_get_bit() for tarvals with any data mode.

In particular this unbreaks dumping boolean bitinfo.

8l/libfirm,jonashaag/libfirm,davidgiven/libfirm,MatzeB/libfirm,MatzeB/libfirm,jonashaag/libfirm,jonashaag/libfirm,davidgiven/libfirm,killbug2004/libfirm,killbug2004/libfirm,libfirm/libfirm,libfirm/libfirm,libfirm/libfirm,8l/libfirm,jonashaag/libfirm,davidgiven/libfirm,jonashaag/libfirm,davidgiven/libfirm,killbug2004/libfirm,8l/libfirm,libfirm/libfirm,MatzeB/libfirm,killbug2004/libfirm,8l/libfirm,jonashaag/libfirm,8l/libfirm,MatzeB/libfirm,davidgiven/libfirm,killbug2004/libfirm,davidgiven/libfirm,8l/libfirm,killbug2004/libfirm,davidgiven/libfirm,libfirm/libfirm,MatzeB/libfirm,jonashaag/libfirm,killbug2004/libfirm,MatzeB/libfirm,MatzeB/libfirm,8l/libfirm