Eliminate unnecessary uses of UMA_ZONE_NOFREE from the swap pager

[alc]

Summary

Passing UMA_ZONE_NOFREE to uma_zcreate() for swpctrie_zone and swblk_zone is redundant, because uma_zone_reserve_kva() is performed on both zones and it sets this same flag on the zone.

Moreover, I don't see why the swap pager would require either zone to be UMA_ZONE_NOFREE.

[kib]

I believe NOFREE there is to reduce risk of the deadlock due to the allocation, and not to prevent memory type change.

[alc]

In D17296#368720, @kib wrote:

I believe NOFREE there is to reduce risk of the deadlock due to the allocation, and not to prevent memory type change.

Me too. I would hope, if not expect, that our use of M_USE_RESERVE on allocations by the page daemon would suffice.