staging/rdma/hfi1: Add credits for VL0 to VL7 in snoop mode

Add a new option to the snoop ioctl which allows credits to be allocated
across all VLs. Previously only VL0 and VL15 had credits allocated.
The new option used in the ioctl HFI1_SNOOP_IOCSET_OPTS allows credits
to be allocated so that VL15 will have at least 8.5KB credits and the
other VLs will have the rest of the credits divided equally across
themselves.

The total number of credits are stored in the upper 16 bits of the
integer passed and the cumulative value should ensure that VL0 has at
least 8.5KB and each VL a minimum of 2KB + 128 bytes

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Reviewed-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Sadanand Warrier <sadanand.warrier@intel.com>
Signed-off-by: Jubin John <jubin.john@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>