gdbserver: remove leftovers from tic6x target_desc selftests

Commit 9a5d3e6c4a50 ("gdb: remove tic6x .dat files") removed the .dat
files that were used solely for selftests in linux-tic6x-low.cc.
However, I forgot to remove the things that depended on that in
linux-tic6x-low.cc (or rather, I put them in the wrong patch).  As-is,
linux-tic6x-low.cc will certainly no build, because function
selftests::tdesc::tic6x_tdesc_test is not defined anywere.  Remove those
remaining bits.

Change-Id: I3f307a6ae4848ef748e2a685a870b662c88180b5
1 file changed