net: dsa: lan9303: Renamed indirect phy access functions

Preparing for the following fix of MDIO phy access:

Renamed functions that access PHY 1 and 2 indirectly through PMI
registers.

 lan9303_port_phy_reg_wait_for_completion() to
 lan9303_indirect_phy_wait_for_completion()

 lan9303_port_phy_reg_read() to
 lan9303_indirect_phy_read()

 lan9303_port_phy_reg_write() to
 lan9303_indirect_phy_write()

Also changed "val" parameter of lan9303_indirect_phy_write() to u16,
for clarity.

Signed-off-by: Egil Hjelmeland <privat@egil-hjelmeland.no>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>