i.MX7ULP: Correct the clock index

On i.MX7ULP, value zero is reserved in SCG1 RCCR register,
so the val should be decreased by 1 to get the correct clock
source index.

Signed-off-by: Bai Ping <ping.bai@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
1 file changed