[gdb/testsuite] Fix gdb.ada/same_enum.exp

[gdb/testsuite] Fix gdb.ada/same_enum.exp

Test-case gdb.ada/same_enum.exp is supposed to be a regression test for this
bit of code in remove_extra_symbols:
...
  if (symbols_are_identical_enums (syms))
    syms.resize (1);
...

The test-case does "print red" and expects one of these two choices to be
picked by remove_extra_symbols:
...
  type Color is (Black, Red, Green, Blue, White);
  type RGB_Color is new Color range Red .. Blue;
...
but because only the type Color is used:
...
  FC : Color := Red;
  SC : Color := Green;
...
the RGB_Color type is eliminated from the debug info, and consequently
remove_extra_symbols has no effect for the test-case.

In other words, we have:
...
(gdb) ptype Color ^M
type = (black, red, green, blue, white)^M
(gdb) ptype RGB_Color^M
No definition of "rgb_color" in current context.^M
...

Fix this by changing the type of SC to RGB_Color, and add prints of the two
types to check that they're both available.

With the test-case fixed, if we disable the bit of code in
remove_extra_symbols we get:
...
(gdb) print red^M
Multiple matches for red^M
[0] cancel^M
[1] pck.color'(pck.red) (enumeral)^M
[2] pck.rgb_colorB'(pck.red) (enumeral)^M
> FAIL: gdb.ada/same_enum.exp: print red (timeout)
...
in other words, the test-case now properly functions as a regression test.

Tested on x86_64-linux.