kernel/pci: Use spin_*() functions directly.
[iwn] Fix required calibration flags for the Centrino 1000 NIC.

Tested with Intel Centrino Wireless-N 1000.

Obtained-From: FreeBSD (commit dd4e54a1ddf657f080a88c674e12459f404dea61)
Fixes: http://bugs.dragonflybsd.org/issues/2720