readelf: Check there is enough data to read DWARF line opcodes arguments.

When reading the debug_line opcode arguments we have to make sure there
is enough data to read the arguments (if there are any(.

The similar code in dwarf_getsrclines already had these checks.

https://sourceware.org/bugzilla/show_bug.cgi?id=24116



Signed-off-by: Mark Wielaard <mark@klomp.org>