ENGR00172222:imx6_defconfig: enable ARM errata software workaround 764369

ENGR00172222:imx6_defconfig: enable ARM errata software workaround 764369

We need enable the following ARM errata software workaround:

    CONFIG_ARM_ERRATA_764369=y

This errata is TKT078684 in i.MX6Q errata list.

In order to enable this errata, we need cherry-pick the following commit:
ARM: 7091/1: errata: D-cache line maintenance operation by MVA may not succeed:
f64f6df4241093ea928b0a263ec53b93b65efc08

In order to apply the above patch successfully and keep the git history, we also
need cherry-pick the following commit:

ARM: pm: add function to set WFI low-power mode for SMP CPUs
292ec42af7c6361435fe9df50cd59ec76f6741c6

These ERRATAs applied to i.MX6Q(cortex-a9:r2p10 smp)

Signed-off-by: Jason Liu <r64343@freescale.com>