ARM: OMAP5: Enable Cortex A15 errata 798181

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

Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>