IB/qib: Change lkey table allocation to support more MRs
The lkey table is allocated with with a get_user_pages() with an
order based on a number of index bits from a module parameter.
The underlying kernel code cannot allocate that many contiguous pages.
There is no reason the underlying memory needs to be physically
contiguous.
This patch:
- switches the allocation/deallocation to vmalloc/vfree
- caps the number of bits to 23 to insure at least 1 generation bit
o this matches the module parameter description