x86: a little bit of 16-bit video mode setting code cleanup

x86: a little bit of 16-bit video mode setting code cleanup

To "compensate" for the code size growth by an earlier change:
- drop "trampoline" labels (in almost all cases the target label is
  reachable with an 8-bit-displacement branch anyway, and a single 16-
  bit-displacement branch is still better than a pair of two branches)
- drop an entirely dead insn from wakeup.S:mode_setw
- reduce code size in a few other (obvious I hope) cases, by more
  suitable insn/operands selection

Also drop redundant #define-s (move suitable #include a little earlier
instead) and add two alignment directives.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>