ASoC: Intel: Skylake: Uninitialized variable in probe_codec()

My static checker complains that if snd_hdac_bus_get_response() returns
-EIO then "res" is uninitialized.  Fix this by initializing it to -1 so
that the error is handled correctly.

Fixes: d8c2dab8 ("ASoC: Intel: Add Skylake HDA audio driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/skylake/skl.c

@@ -512,7 +512,7 @@ static int probe_codec(struct hdac_ext_bus *ebus, int addr)
 	struct hdac_bus *bus = ebus_to_hbus(ebus);
 	unsigned int cmd = (addr << 28) | (AC_NODE_ROOT << 20) |
 		(AC_VERB_PARAMETERS << 8) | AC_PAR_VENDOR_ID;
-	unsigned int res;
+	unsigned int res = -1;
 
 	mutex_lock(&bus->cmd_mutex);
 	snd_hdac_bus_send_cmd(bus, cmd);