IB/qib: Set cfgctxts to number of CPUs by default

Up to now, we have set the number of available user contexts based on
the number of hardware contexts which is set according to the number
of available CPUs.  This was fine since most CPUs had a power of two
number of cores and the chip supported 4, 8, or 16 user contexts.  Now
that some systems have 12 cores, the default isn't optimal and should
be set to 12 even though 16 hardware contexts need to be enabled.

Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>