remoteproc: Fix remaining wrong return formatting in documentation

kernel documentation specification:
"The return value, if any, should be described in a dedicated section
named Return."
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211206191858.10741-1-arnaud.pouliquen@foss.st.comSigned-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/remoteproc/mtk_scp_ipi.c

@@ -23,7 +23,7 @@
  *
  * Register an ipi function to receive ipi interrupt from SCP.
  *
- * Returns 0 if ipi registers successfully, -error on error.
+ * Return: 0 if ipi registers successfully, -error on error.
  */
 int scp_ipi_register(struct mtk_scp *scp,
 		     u32 id,
@@ -150,7 +150,7 @@ EXPORT_SYMBOL_GPL(scp_ipi_unlock);
  * When the processing completes, IPI handler registered
  * by scp_ipi_register will be called in interrupt context.
  *
- * Returns 0 if sending data successfully, -error on error.
+ * Return: 0 if sending data successfully, -error on error.
  **/
 int scp_ipi_send(struct mtk_scp *scp, u32 id, void *buf, unsigned int len,
 		 unsigned int wait)

drivers/remoteproc/st_slim_rproc.c

@@ -216,7 +216,7 @@ static const struct rproc_ops slim_rproc_ops = {
  * obtains and enables any clocks required by the SLIM core and also
  * ioremaps the various IO.
  *
- * Returns st_slim_rproc pointer or PTR_ERR() on error.
+ * Return: st_slim_rproc pointer or PTR_ERR() on error.
  */
 
 struct st_slim_rproc *st_slim_rproc_alloc(struct platform_device *pdev,