visorbus: fix uninitialized variable access

The setup_crash_devices_work_queue function only partially initializes
the message it sends to chipset_init, leading to undefined behavior:

drivers/visorbus/visorchipset.c: In function 'setup_crash_devices_work_queue':
drivers/visorbus/visorchipset.c:333:6: error: '((unsigned char*)&msg.hdr.flags)[0]' is used uninitialized in this function [-Werror=uninitialized]
  if (inmsg->hdr.flags.response_expected)

Set up the entire structure, zero-initializing the 'response_expected'
flag.

This was apparently found by the patch that added the -O3 build option
in Kconfig.

Fixes: 12e364b9f0 ("staging: visorchipset driver to provide registration and other services")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200107202950.782951-1-arnd@arndb.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/visorbus/visorchipset.c

@@ -1210,14 +1210,17 @@ static void setup_crash_devices_work_queue(struct work_struct *work)
 {
 	struct controlvm_message local_crash_bus_msg;
 	struct controlvm_message local_crash_dev_msg;
-	struct controlvm_message msg;
+	struct controlvm_message msg = {
+		.hdr.id = CONTROLVM_CHIPSET_INIT,
+		.cmd.init_chipset = {
+			.bus_count = 23,
+			.switch_count = 0,
+		},
+	};
 	u32 local_crash_msg_offset;
 	u16 local_crash_msg_count;
 
 	/* send init chipset msg */
-	msg.hdr.id = CONTROLVM_CHIPSET_INIT;
-	msg.cmd.init_chipset.bus_count = 23;
-	msg.cmd.init_chipset.switch_count = 0;
 	chipset_init(&msg);
 	/* get saved message count */
 	if (visorchannel_read(chipset_dev->controlvm_channel,