platform/chrome: cros_ec_lpc: Use DEFINE_MUTEX() for mutex lock

mutex lock can be initialized automatically with DEFINE_MUTEX()
rather than explicitly calling mutex_init().
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NYe Bin <yebin10@huawei.com>
Signed-off-by: NEnric Balletbo i Serra <enric.balletbo@collabora.com>
Link: https://lore.kernel.org/r/20210409095138.2293869-1-yebin10@huawei.com

drivers/platform/chrome/cros_ec_lpc_mec.c

@@ -14,7 +14,7 @@
  * This mutex must be held while accessing the EMI unit. We can't rely on the
  * EC mutex because memmap data may be accessed without it being held.
  */
-static struct mutex io_mutex;
+static DEFINE_MUTEX(io_mutex);
 static u16 mec_emi_base, mec_emi_end;
 
 /**
@@ -142,7 +142,6 @@ EXPORT_SYMBOL(cros_ec_lpc_io_bytes_mec);
 
 void cros_ec_lpc_mec_init(unsigned int base, unsigned int end)
 {
-	mutex_init(&io_mutex);
 	mec_emi_base = base;
 	mec_emi_end = end;
 }