Instead of accessing the rate field of the static
clock devices directly, use the recently introduced
helper function to get the rate of the basic clocks.

The static ath79_{ahb,cpu,ddr,ref}_clk variables
will be removed by a subsequent patch. The actual
change is in preparation of that.

Also move the clock frequency printing code into
the plat_time_init function. We are getting the
cpu clock rate there already so we can save an
extra call of the helper.
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5782/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>