remoteproc: add is_iomem to da_to_va

Introduce an extra parameter is_iomem to da_to_va, then the caller
could take the memory as normal memory or io mapped memory.

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/1615029865-23312-5-git-send-email-peng.fan@oss.nxp.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>