ARM: DRA7: Enable Cortex A15 errata 798181

ARM errata 798181 is applicable for OMAP5/DRA7 based devices. So enable
the same in the build.

DRA7xx is based on Cortex-A15 r2p2 revision.

ARM Errata extract and workaround information is as below.

On Cortex-A15 (r0p0..r3p2) the TLBI*IS/DSB operations are not
adequately shooting down all use of the old entries. The
ARM_ERRATA_798181 option enables the Linux kernel workaround
for this erratum which sends an IPI to the CPUs that are running
the same ASID as the one being invalidated.

Signed-off-by: Praneeth Bajjuri <praneeth@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>