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: NJoel Stanley <joel@jms.id.au>
Tested-by: NAndrew Jeffery <andrew@aj.id.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>