net: phy: realtek: Modify 2.5G PHY name to RTL8226

Realtek single-chip Ethernet PHY solutions can be separated as below:
10M/100Mbps: RTL8201X
1Gbps: RTL8211X
2.5Gbps: RTL8226/RTL8221X
RTL8226 is the first version for realtek that compatible 2.5Gbps single PHY.
Since RTL8226 is single port only, realtek changes its name to RTL8221B from
the second version.
PHY ID for RTL8226 is 0x001cc800 and RTL8226B/RTL8221B is 0x001cc840.

RTL8125 is not a single PHY solution, it integrates PHY/MAC/PCIE bus
controller and embedded memory.

Signed-off-by: Willy Liu <willy.liu@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>