cli_classic: Tidy up some repeated handling patterns into funcs

Introduce cli_classic_single_operation() to consolidate the repeating
pattern of multiple CLI operations at once. Also modify
cli_classic_abort_usage() to take an optional error abort string and
print it to stderr, this allows for trimming a few more lines off the
cli implementation.

V.2: A few fixes upon review:
  - Trim off some unnecessary braces for single line branches.
  - Pass 'operation_specified' by reference.
  - Rename a function.
V.3: Fix print order of cli_classic_abort_usage().

Change-Id: I54598efdaee2b95cb278b0f2aac05f48bbd95bef
Signed-off-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/35611


Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>