Since UMA_ZONE_NOFREE is specified when l2zone and l2table_zone are created,
there is no need to release and reacquire the pmap and pvh global locks
around calls to uma_zfree(). Recursion into the pmap simply won't occur.

Eliminate the use of M_USE_RESERVE. It is deprecated and, in fact, counter-
productive, meaning that it actually makes the memory allocation request
more likely to fail.

Eliminate the macros pmap_{alloc,free}_l2_dtable(). They are of limited
utility, and pmap_free_l2_dtable() was inconsistently used.

Tidy up pmap_init(). In particular, change the initialization of the PV
zone so that it doesn't span the initialization of the l2 and l2table zones.

Tested by: jmg