sfc: remove phy_op indirection

Originally there were several implementations of PHY operations for the
 several different PHYs used on Falcon boards.  But Falcon is now in a
 separate driver, and all sfc NICs since then have had MCDI-managed PHYs.
Thus, there is no need to indirect through function pointers in
 efx->phy_op; we can simply call the efx_mcdi_phy_* functions directly.

This also hooks up these functions for EF100, which was previously using
 the dummy_phy_ops.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>