msm: smcmod: Flush the ion buffers prior to scm_call

The scm_call function in scm.c will be changing to only flush the
command buffer area instead of the entire cache.  Flush the input
ion buffers using msm_ion_do_cache_op.

The private function used to invalidate response buffers returned
from scm_call is replaced with a call to msm_ion_do_cache_op for
consistency.

The temporary smcmod_scm_call function is removed in favor of
directly calling scm_call.

Change-Id: Iacb2dc3d027382a89575ae8135ab612f9a515394
Acked-by: Jennifer Zenner <jzenner@qti.qualcomm.com>
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>