fbdev: drop res_id parameter from remove_conflicting_pci_framebuffers

Since commit b0e999c9 ("fbdev: list all pci memory bars as
conflicting apertures") the parameter was used for some sanity checks
only, to make sure we detect any issues with the new approach to just
list all memory bars as apertures.

No issues turned up so far, so continue to cleanup:  Drop the res_id
parameter, drop the sanity checks.  Also downgrade the logging from
"info" level to "debug" level and update documentation.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20190822090645.25410-2-kraxel@redhat.com