remoteproc: stm32: Introduce new attach() operation

Introduce new attach function to be used when attaching to a
remote processor.

Mainly based on the work published by Arnaud Pouliquen [1].

[1]. https://patchwork.kernel.org/project/linux-remoteproc/list/?series=239877

Acked-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200714200445.1427257-11-mathieu.poirier@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/stm32_rproc.c

@@ -460,6 +460,13 @@ static int stm32_rproc_start(struct rproc *rproc)
 	return stm32_rproc_set_hold_boot(rproc, true);
 }
 
+static int stm32_rproc_attach(struct rproc *rproc)
+{
+	stm32_rproc_add_coredump_trace(rproc);
+
+	return stm32_rproc_set_hold_boot(rproc, true);
+}
+
 static int stm32_rproc_stop(struct rproc *rproc)
 {
 	struct stm32_rproc *ddata = rproc->priv;
@@ -525,6 +532,7 @@ static void stm32_rproc_kick(struct rproc *rproc, int vqid)
 static struct rproc_ops st_rproc_ops = {
 	.start		= stm32_rproc_start,
 	.stop		= stm32_rproc_stop,
+	.attach		= stm32_rproc_attach,
 	.kick		= stm32_rproc_kick,
 	.load		= rproc_elf_load_segments,
 	.parse_fw	= stm32_rproc_parse_fw,