debug: coredump: coredump_backend_flash: Keep error in context on flush

Do not override the last known value in backend_ctx.error with the result
of flushing.
Any previous error would be cleared and the coredump would appear to have
succeeded.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>

Author: pdgendt

subsys/debug/coredump/coredump_backend_flash_partition.c

@@ -468,9 +468,11 @@ static void coredump_flash_backend_end(void)
 	}
 
 	/* Flush buffer */
-	backend_ctx.error = stream_flash_buffered_write(
-				&backend_ctx.stream_ctx,
-				stream_flash_buf, 0, true);
+	ret = stream_flash_buffered_write(&backend_ctx.stream_ctx, stream_flash_buf, 0, true);
+	if (ret != 0) {
+		LOG_ERR("Cannot flush coredump stream (%d)", ret);
+		backend_ctx.error = ret;
+	}
 
 	/* Write header */
 	hdr.size = stream_flash_bytes_written(&backend_ctx.stream_ctx);