arch: arm: Use dsb instruction for data barrier

Use dsb instruction for data barriers for cache clean, invalidate
functions instead of cp15 instruction. With Armv8 by default disables
cp15 barriers, if attempted to execute these cp15 barriers we end up in
undefined behaviour.

Change-Id: I3a6dcd350d07d6dbaaca28e841da6e6ada973cda
1 file changed