[gdb/testsuite] Fix end_sequence addresses

[gdb/testsuite] Fix end_sequence addresses

I noticed in test-case gdb.reverse/map-to-same-line.exp, that the end of main:
...
00000000004102c4 <end_of_sequence>:
  4102c4:       52800000        mov     w0, #0x0                        // #0
  4102c8:       9100c3ff        add     sp, sp, #0x30
  4102cc:       d65f03c0        ret
...
is not described by the line table:
...
File name                    Line number    Starting address    View    Stmt
  ...
map-to-same-line.c                    54            0x4102ac               x
map-to-same-line.c                     -            0x4102c4
...

Fix this by ending the line table at $main_end.

Likewise in a few other test-cases, found using:
...
$ find gdb/testsuite/ -type f \
  | xargs grep -B1 DW_LNE_end_sequence \
  | grep set_address \
  | egrep -v "_end|_len"
...

Tested on aarch64-linux.