IB/mthca: Use DEFINE_MUTEX() instead of mutex_init()

mthca_device_mutex() can be initialized automatically with
DEFINE_MUTEX() rather than explicitly calling mutex_init().  This
saves a bit of text and shrinks the source by a line, so we may as
well do it....
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mthca/mthca_main.c

@@ -80,7 +80,7 @@ static int tune_pci = 0;
 module_param(tune_pci, int, 0444);
 MODULE_PARM_DESC(tune_pci, "increase PCI burst from the default set by BIOS if nonzero");
 
-struct mutex mthca_device_mutex;
+DEFINE_MUTEX(mthca_device_mutex);
 
 #define MTHCA_DEFAULT_NUM_QP            (1 << 16)
 #define MTHCA_DEFAULT_RDB_PER_QP        (1 << 2)
@@ -1362,8 +1362,6 @@ static int __init mthca_init(void)
 {
 	int ret;
 
-	mutex_init(&mthca_device_mutex);
-
 	mthca_validate_profile();
 
 	ret = mthca_catas_init();