sfc: SFT9001/SFN4111T: Check PHY boot status during board initialisation

During SFN4111T initialisation, check whether the PHY boot status
indicates a bad firmware checksum.  If so, prepare to reflash rather
than continuing with normal initialisation.

Remove redundant PHY boot status check from tenxpress_phy_init().

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