sfc: SFT9001: Fix condition for LNPGA power-off

Only the SFX7101 requires software power control.  This was
incorrectly being applied to the SFT9001 rev A as well.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>