cpu: imx8: fix type and rate detection

CPU type and rate detection is broken, for A35 cpu we get A53:
...
sc_pm_get_clock_rate: resource:0 clk:2: res:3
Could not read CPU frequency: -22
CPU:   NXP i.MX8QXP RevB A53 at 0 MHz at 47C

Fixes: 55bc96f3 ("cpu: imx8: fix get core name and rate")
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Reviewed-by: Peng Fan <peng.fan@nxp.com>