[gdb/testsuite] Fix ERROR in gdb.dwarf2/dw2-out-of-range-end-of-seq.exp

When running test-case gdb.dwarf2/dw2-out-of-range-end-of-seq.exp on a
system with debug packages installed, I run into:
...
(gdb) maint info line-table^M
  ... <lots of output> ...
ERROR: internal buffer is full.
UNRESOLVED: gdb.dwarf2/dw2-out-of-range-end-of-seq.exp: \
  END with address 1 eliminated
...

Fix this by limiting the output of the command using a regexp.

I also noticed that when making the regexp match nothing, meaning
the command has no output, the test didn't FAIL.  Fixed this by adding a
PASS pattern.

I also noticed that the FAIL pattern didn't work with -m32, fixed that as
well.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2021-01-28  Tom de Vries  <tdevries@suse.de>

	* gdb.dwarf2/dw2-out-of-range-end-of-seq.exp: Add regexp to
	"maint info line-table".  Make PASS pattern more specific.  Make
	FAIL pattern work for -m32.