imx: mx6: Change the get_ipg_per_clk for OSC 24Mhz source

For MX6SL and MX6SX, the perclk can come from OSC 24Mhz source. Fix
the get_ipg_per_clk function to support it.

Signed-off-by: Ye.Li <B37916@freescale.com>
1 file changed