[test][llvm-dwarfdump] Normalise contents and checks for line tables

The line tables in debug_line_malformed.s had contents that varied more
than was necessary for the testing, making it harder to follow what was
important. This patch normalises them so that they all share
more-or-less the same body. Additionally, it makes the testing for what
was printed more consistent, to show that the right parts of the line
table prologue and body are/are not parsed and printed.

Reviewed By: JDevlieghere

Differential Revision: https://reviews.llvm.org/D71755