cpufreq: imx6q: add 696MHz operating point for i.mx6ul

Add 696MHz operating point for i.MX6UL, only for those
parts with speed grading fuse set to 2b'10 supports
696MHz operating point, so, speed grading check is also
added for i.MX6UL in this patch, the clock tree for each
operating point are as below:

696MHz:
    pll1                       696000000
       pll1_bypass             696000000
          pll1_sys             696000000
             pll1_sw           696000000
                arm            696000000
528MHz:
    pll2                       528000000
       pll2_bypass             528000000
          pll2_bus             528000000
             ca7_secondary_sel 528000000
                step           528000000
                   pll1_sw     528000000
                      arm      528000000
396MHz:
    pll2_pfd2_396m             396000000
       ca7_secondary_sel       396000000
          step                 396000000
             pll1_sw           396000000
                arm            396000000
198MHz:
    pll2_pfd2_396m             396000000
       ca7_secondary_sel       396000000
          step                 396000000
             pll1_sw           396000000
                arm            198000000

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>