irqchip/gic-v3-mbi: Fix uninitialized mbi_lock

The mbi_lock mutex is left uninitialized, so let's use DEFINE_MUTEX
to initialize it statically.

Fixes: 50528752 ("irqchip/gic-v3: Add support for Message Based Interrupts as an MSI controller")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-gic-v3-mbi.c

@@ -24,7 +24,7 @@ struct mbi_range {
 	unsigned long		*bm;
 };
 
-static struct mutex		mbi_lock;
+static DEFINE_MUTEX(mbi_lock);
 static phys_addr_t		mbi_phys_base;
 static struct mbi_range		*mbi_ranges;
 static unsigned int		mbi_range_nr;