I believe this same warning was produced when building th "stock" TI kernel from the SDK (version 7):
warning: (SOC_OMAP5 && SOC_DRA7XX) selects ARM_ERRATA_799270 which has unmet direct dependencies (CPU_V7 && SMP)
The kernel seems to work properly, so I'm not sure if this is something to be concerned about or not.
CPU_V7 is enabled, but SMP is not - and the AM3358 that we're using is a single-core processor. I suspect this is innocuous, but it would be nice to know for sure.