staging/rdma/hfi1: Fix for module parameter rcvhdrcnt when it's 2097152

The driver crashes when loaded with parameter rcvhdrcnt=2097152.
The root cause was that rcvhdrcnt was initially a 32 bit variable
and its value was assigned to a 16 bit variable, truncating the
upper 16 bits. This patch prevents the user from passing a value
for rcvhdrcnt greater than 16352 (Maximum number for rcvhdrcnt).

Reviewed-by: Dean Luick <dean.luick@intel.com>
Reviewed-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Sebastian Sanchez <sebastian.sanchez@intel.com>
Signed-off-by: Jubin John <jubin.john@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>