ENGR00303122-3 ARM: imx6sx: fix ASRC related clocks in the clock tree

ENGR00303122-3 ARM: imx6sx: fix ASRC related clocks in the clock tree

According to imx6sx RM, there are three clock providers for ASRC:
	Module clock    Clock root      Gate
	asrck_clock_d   spdif0_clk_root N/A
	ipg_clk         ahb_clk_root    asrc_clk_enable
	mem_clk         ahb_clk_root    asrc_clk_enable

while the current clock tree describes a clock named 'ASRC' that only
describes the asrc_clk_enable function.

Thus this patch first adds the other missing clocks to ASRC.

[ Since we don't have the gate for asrck_clock_d, we can pass spdif0_clk
  to ASRC in the devicetree directly. ]

Signed-off-by: Nicolin Chen <Guangyu.Chen@freescale.com>