ARM: dove: unify clock setup

This patch synchronizes the clock setup of dove with other orion-based
platforms.

In dove_find_tclk there was a note about DOVE_SAMPLE_HI/LO register to
detect tclk. While it might be possible to set a different tclk frequency
with reset strapping the Dove datasheets don't tell anything about tclk
frequency here. Therefore, I removed that comment.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>