nvme: Use saved mps when initializing drive

Make sure we set the MPS we cached (currently the drives minimum mps) in
CC (Controller Configuration) when reinitializing the drive. It must
match the page_size that we're going to use. Also retire less specific
NVME_PAGE_SHIFT since it's now unused.

Sponsored by: Netflix
Reviewed by: chuck
Differential Revision: https://reviews.freebsd.org/D34869