Only check the ProducerConsumer flag on extended memory. As per the ACPI
6.0 spec 6.4.3.5 bit 0 is ignored on QWord, DWord, and Word Address Space
Descriptors, but not Extended Address Space Descriptors.

Reviewed by: jhb
Sponsored by: DARPA, AFRL
Sponsored by: Cavium (Hardware)
Differential Revision: https://reviews.freebsd.org/D14516