Revert "arm64: mm: Modify __flush_dcache_op"

Revert "arm64: mm: Modify __flush_dcache_op"

This reverts commit ac511b3c4f44d13c47996a1771b44b2e7698dc10.

Reverting as this can cause only cache clean when cache flush
is required. Also, it is observed that most of the time taken
during cache flush was due to context switch to interrupt context.
This change does not fix that issue.

Bug 200035864

Change-Id: I676e1f0e9672348040ca106c21108186ffb51696
Signed-off-by: Sri Krishna chowdary <schowdary@nvidia.com>
Reviewed-on: http://git-master/r/556686
GVS: Gerrit_Virtual_Submit
Reviewed-by: Krishna Reddy <vdumpa@nvidia.com>