LinuxKPI: pci.h split up pcim_iomap_regions_request_all()

Factor out parts of pcim_iomap_regions_request_all() into
pcim_iomap_regions() now needed for a driver.

Sponsored by: The FreeBSD Foundation
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D36654

(cherry picked from commit 30048f61423bed87912686a7adfd12be9a4c7c27)