common/sfc_efx/base: merge versions of init EvQ wrappers

common/sfc_efx/base: merge versions of init EvQ wrappers

The decision on which version of the INIT_EVQ command to use may
be done inside the function itself. Caller should just provide
enough information sufficient in both cases. It avoids code
duplication and simplifies maintenance.

If v2 is not supported, keep decision about low-latency hint outside
the MCDI helper function since it will differ on Riverhead (there is
no EVB yet, but still want merging for better throughput).

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Andy Moreton <amoreton@xilinx.com>