PM / AVS: check initial rate only once

PM / AVS: check initial rate only once

The patch fixes the warring when rk3399-vr resume:

CPU4: found redistributor 100 region 0:0x00000000fef80000
CPU4: update cpu_capacity 1024
CPU4: Booted secondary processor [410fd082]
rk3x-i2c ff3c0000.i2c: timeout, ipd: 0x10, state: 1
rk3x-i2c ff3c0000.i2c: timeout, ipd: 0x10, state: 1
rk3x-i2c ff3c0000.i2c: timeout, ipd: 0x10, state: 1
cpu cpu4: _set_opp_voltage:
failed to set voltage (800000 800000 800000 mV): -110
cpu cpu4: failed to set volt 800000
CPU4 is up
Detected PIPT I-cache on CPU5
CPU5: found redistributor 101 region 0:0x00000000fefa0000
CPU5: update cpu_capacity 1024
CPU5: Booted secondary processor [410fd082]
CPU5 is up

Change-Id: I36f1b5d23c8d2436e20765d699dfde9eb8cf74fa
Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>