net: ftgmac100: Request clock and set speed

net: ftgmac100: Request clock and set speed

According to the ASPEED datasheet, gigabit speeds require a clock of
100MHz or higher. Other speeds require 25MHz or higher. This patch
configures a 100MHz clock if the system has a direct-attached
PHY, or 25MHz if the system is running NC-SI which is limited to 100MHz.

There appear to be no other upstream users of the FTGMAC100 driver it is
hard to know the clocking requirements of other platforms. Therefore a
conservative approach was taken with enabling clocks. If the platform is
not ASPEED, both requesting the clock and configuring the speed is
skipped.

Signed-off-by: Joel Stanley <[email protected]>
Tested-by: Andrew Jeffery <[email protected]>
Signed-off-by: David S. Miller <[email protected]>