[gdb/testsuite] Fix gdb.dwarf2/dw2-fixed-point.exp on arm-linux

[gdb/testsuite] Fix gdb.dwarf2/dw2-fixed-point.exp on arm-linux

With test-case gdb.dwarf2/dw2-fixed-point.exp on arm-linux I run into:
...
(gdb) PASS: gdb.dwarf2/dw2-fixed-point.exp: set lang ada
print pck.fp1_var^M
$1 = 0.3125^M
(gdb) FAIL: gdb.dwarf2/dw2-fixed-point.exp: print pck.fp1_var
...

The problem is that the thumb prologue analyzer overshoot, setting the
breakpoint for main after line 49:
...
    46  int
    47  main (void)
    48  {
    49    pck__fp1_var++;
...
and consequently we see the value of pck.fp1_var after line 49 instead of
before line 49.  This is PR tdep/31981.

Work around this by removing line 49 and all similar subsequent lines, which
turn out to be dead code.

Approved-By: Luis Machado <luis.machado@arm.com>
Tested on arm-linux.