Use pmap_qenter in the N1SDP PCIe driver

In the Neoverse N1 SDP PCIe driver we need to map a page shared
between the firmware and the kernel. Previously we would use
pmap_kenter for this, however as this is not standardised between
architectures switch to the common pmap_qenter.

While here fix the error handling code to clean up on failure.

Reviewed by: br
Sponsored by: Innovate UK
Differential Revision: https://reviews.freebsd.org/D28890