MLK-10257-02 arm: imx7: Change the clks tree setting used by A7 core

The A7 core clock can't be gated and when changing the A7 core clock rate
dynamically, if the clks on the A7 core path with SET_RATE_GATE flag set,
it will fail. So the the SET_RATE_GATE need not be set.

Signed-off-by: Bai Ping <b51503@freescale.com>