ARM: imx5: drop arguments from mx5_clocks_common_init()

The function mx5_clocks_common_init() was created with a number of
arguments to pass oscillator clock rate in non-DT boot.  Since i.MX5
is DT only platform, the arguments can be dropped, and the clock rate
can just be retrieved from device tree.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>