net: dsa: qca8k: enlarge mdio delay and timeout

The witch require some extra delay after setting page or the next
read/write can use still use the old page. Add a delay after the
set_page function to address this as it's done in QSDK legacy driver.
Some timeouts were notice with VLAN and phy function, enlarge the
mdio busy wait timeout to fix these problems.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>