firmware: google: framebuffer: Tie platform device to PCI hardware

firmware: google: framebuffer: Tie platform device to PCI hardware

Use the PCI device as parent of the system-framebuffer device instead
of the coreboot device. Prevents SIGBUS or SIGSEG after hot-unplug of
the PCI device while the framebuffer is active.

The simple-framebuffer device depends on the PCI hardware, so this
device needs to be its parent. The current coreboot parent is no
longer needed after the system-framebuffer device has been created.

On systems without PCI or if no PCI parent device could be found,
the platform device hangs on the platform bus directly.

The fix here is similar to code in sysfb, which contained that same
bug.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Tzung-Bi Shih <tzungbi@kernel.org>
Acked-by: Julius Werner <jwerner@chromium.org>
Link: https://patch.msgid.link/20260217155836.96267-5-tzimmermann@suse.de