drm/bochs: downgrade pci_request_region failure from error to warning

Shutdown of firmware framebuffer has a bunch of problems.  Because
of this the framebuffer region might still be reserved even after
drm_fb_helper_remove_conflicting_pci_framebuffers() returned.

Don't consider pci_request_region() failure for the framebuffer
region as fatal error to workaround this issue.

Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20200313084152.2734-1-kraxel@redhat.com