cli_classic.c: Make -r/-w/-v argument optional when using -i

Make the filename parameter directly following -r/-w/-v optional, since
the -i parameter allows the image to be written to be sourced from
multiple files, regions to be read from flash and written to separate
image files, and regions to be verified using an image file only
containing that region.

Since the filename parameter following -w/-v was ignored when a
filename was specified following `-i <region>:<filename>`, this patch
essentially removes the requirement to provide an unused parameter.

Based on https://review.coreboot.org/c/flashrom/+/52362.

TEST=run the following commands on a supported board:
flashrom -p internal -r /tmp/coreboot.rom
flashrom -p internal -r --ifd -i bios:/tmp/coreboot.rom
flashrom -p internal -r /tmp/coreboot.rom --ifd -i bios:/tmp/bios.bin
flashrom -p internal -w /tmp/coreboot.rom
flashrom -p internal -w --ifd -i bios:/tmp/coreboot.rom
flashrom -p internal -w /tmp/coreboot.rom --ifd -i bios:/tmp/bios.bin
flashrom -p internal -v /tmp/coreboot.rom
flashrom -p internal -v --ifd -i bios:/tmp/coreboot.rom
flashrom -p internal -v /tmp/coreboot.rom --ifd -i bios:/tmp/bios.bin

Change-Id: I6eba095d478f1a7bdbc3854627a656f93dd9e452
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
---
M cli_classic.c
M doc/classic_cli_manpage.rst
M include/layout.h
M layout.c
4 files changed, 123 insertions(+), 23 deletions(-)