If we already encountered the last extended capability in the
list, we'd call pciexp_get_ext_cap_offset() with `offset == 0`.
So it also needs to check if the passed offset is valid.
As there were no callers of pciexp_find_next_extended_cap()
yet, pciexp_get_ext_cap_offset() was only ever called with
`PCIE_EXT_CAP_OFFSET`.
Change-Id: I155c4691a34ff16661919913a3446fa915ac535e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66452
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Bill XIE <persmule@hardenedlinux.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
4b864e5c30