bnxt_en: Assign more RSS context resources to the VFs.

The driver currently only assignes 1 RSS context to each VF.  This works
for the Linux VF driver.  But other drivers, such as DPDK, can make use
of additional RSS contexts.  Modify the code to divide up and assign
RSS contexts to VFs just like other resources.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>