nvme_ctrlr_enable: Remove delays

[imp]

Summary

Remove delays after writing the administrative queue registers. These
delays are from the very earliest days of the driver (they are in the
first commit) and were most likely vestiges of the Chatham NVMe
prototype card that was used to create this driver. Many of the
workarounds necessary for it aren't necessary for standards compliant
cards. The original driver had other areas marked for Chatham, but these
were not. They are unneeded. There's three lines of supporting evidence.

First, the NVMe standards make no mention of a delay time after these
registers are written. Second, the Linux driver doesn't have them, even
as an option. Third, all my nvme cards work w/o them.

To be safe, add a write barrier between setting up the admin queue and
enabling the controller.

[mav]

I also don't see a point in DELAY()'s. Just thinking would it be right to use bus_space_barrier() before cc write for some non-x86, since it depends on the other registers state?

[imp]

add barrier

[cperciva]

Doesn't build for me.

sys/dev/nvme/nvme_ctrlr.c

58

--- nvme_ctrlr.o ---
/usr/src/sys/dev/nvme/nvme_ctrlr.c:60:11: error: too few arguments to function call, expected 5, have 4
            flags);
                 ^
./x86/bus.h:1002:1: note: 'bus_space_barrier' declared here
bus_space_barrier(bus_space_tag_t tag __unused, bus_space_handle_t bsh __unused,
^

[imp]

sys/dev/nvme/nvme_ctrlr.c

58

I'm an idiot... I got this too, fix it, but somehow uploaded the wrong one :(

[imp]

this time with right barrier