LinuxKPI: add general module_driver(), use it for module_pci_driver()

Factor out module_pci_driver() from 366d68f283793 into a general
module_driver() so other bus attachments can also use the same kind
of macro without duplicating all the lines.

Redefine module_pci_driver() using the new general macro.

No functional changes intended.

Sponsored by: The FreeBSD Foundation
Reviewed by: manu
Differential Revision: https://reviews.freebsd.org/D46467

(cherry picked from commit f5c7feee7129dc88a2e5dc3ce0a075cb5e4f534a)