net/sfc: use adaptive table entry count in flow action RSS

net/sfc: use adaptive table entry count in flow action RSS

Currently, every RSS context uses 128 indirection entries in
the hardware. That is not always optimal because the entries
come from a pool shared among all PCI functions of the board,
while the format of action RSS allows to pass less queue IDs.

With EF100 boards, it is possible to decide how many entries
to allocate for the indirection table of a context. Make use
of that in order to optimise resource usage in RSS scenarios.

Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Reviewed-by: Andy Moreton <amoreton@xilinx.com>