PCI_IRQ_LEGACY was added in 366d68f283 (likely) for rtw88 only.
The define now got renamed and I cannot find any other use but
rtw88 and rtw89.
We keep the old name as comapt while driver updates are in
progress enabling it defining LINUXKPI_VERSION for the two drivers.
Sponsored by; The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D46822
(cherry picked from commit 157e93e0e8138fbaa6ab5d5b20b0c23f903667a6)