Use the right dwarf attributes for parsing location list entries (fixup for r285441)

Note that the parsing code here is still incorrect wrt. the new draft of the
dwarf 5 spec (seconds arguments to DW_LLE_startx_length should be uleb128, not
u32). Once we have compilers actually emitting dwarf conformant with the new
spec, we'll need to revisit this and figure out the proper behavior there.

This should unbreak the linux bot.

llvm-svn: 285562