On Samsung Chromebook Plus (v1), messages and prompts printed during an
initramfs run aren't visible to the user unless the pwm_bl, rockchipdrm,
pwm-cros-ec and panel-simple modules are included. This commit includes
these when MODULES=dep and when MODULES=most.

For MODULES=dep: adds backlight and pwm to the dep_modules_add sys-walk.
Walking backlight includes pwm_bl and pwm includes pwm-cros-ec. Since
panel-simple isn't reachable from /sys/class/**, but it can be reached
from /sys/devices/platform/edp-panel, that path is sys-walked if it
exists.

When {efi,platform,simple,vesa}-framebuffer cannot provide a working
framebuffer device, graphics is sys-walked as well. Walking drm works
for rockchipdrm too, but also includes panfrost, so graphics was chosen
instead.

For MODULES=most: the modules are included in a new case 'fb' in the
auto_add_modules intended for modules providing framebuffer support
for machines where generic drivers don't provide one.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>