net: mvpp2: add hw_version field in "struct mvpp2"

In preparation to the introduction for the support of PPv2.2 in the
mvpp2 driver, this commit adds a hw_version field to the struct
mvpp2, and uses the .data field of the DT match table to fill it in.

Having the MVPP21 and MVPP22 definitions available will allow to start
adding the necessary conditional code to support PPv2.2.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>