net: dsa: felix: attempt to initialize internal hsio plls

The VSC7512 and VSC7514 have internal PLLs that can be used to control
different peripherals. Initialize these high speed I/O (HSIO) PLLs when
they exist, so that dependent peripherals like QSGMII can function.

Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
Signed-off-by: David S. Miller <davem@davemloft.net>