ARM: i.MX clk pllv1: move mxc_decode_pll code to its user

The only code using mxc_decode_pll is clk-pllv1.c, so move the code
there.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Mike Turquette <mturquette@linaro.org>