ARM i.MX6q: Fix periph_clk2_sel and periph2_clk2_sel clocks

The periph_clk2_sel mux can be set to pll3, osc/pll1_ref_clk, or osc/
pll2_burn_in_clk. The periph2_clk2_sel mux can be set to pll3 or pll2.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>