remoteproc: Add kernel-doc comment for is_iomem

Add a kernel-doc comment for the is_iomem function argument in
rproc_da_to_va(). This fixes a warning generated when building
the remoteproc_core with W=1,
  warning: Function parameter or member 'is_iomem' not described in 'rproc_da_to_va'
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suman Anna <s-anna@ti.com>
Link: https://lore.kernel.org/r/20210519180304.23563-2-s-anna@ti.comSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -165,6 +165,7 @@ EXPORT_SYMBOL(rproc_va_to_pa);
  * @rproc: handle of a remote processor
  * @da: remoteproc device address to translate
  * @len: length of the memory region @da is pointing to
+ * @is_iomem: optional pointer filled in to indicate if @da is iomapped memory
  *
  * Some remote processors will ask us to allocate them physically contiguous
  * memory regions (which we call "carveouts"), and map them to specific