[PATCH v2] net: xgmac: Augment mdio read/write with cl-45 format support

[Ng, Boon Khai]

> Currently, clause-22 format is supported. This change adds support for clause-45
> format.
> 
> Signed-off-by: Nikunj Kela <nikunj.kela at sima.ai>
> ---
> Changes in v2:
> 	- Created separate function for configuring clause format

Reviewed-by: Boon Khai Ng <boon.khai.ng at altera.com>
Tested-by: Boon Khai Ng <boon.khai.ng at altera.com>