powerpc/imc-pmu: Use the correct spinlock initializer.

The macro __SPIN_LOCK_INITIALIZER() is implementation specific. Users
that desire to initialize a spinlock in a struct must use
__SPIN_LOCK_UNLOCKED().

Use __SPIN_LOCK_UNLOCKED() for the spinlock_t in imc_global_refc.

Fixes: 76d588dddc459 ("powerpc/imc-pmu: Fix use of mutex in IRQs disabled section")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230309134831.Nz12nqsU@linutronix.de

arch/powerpc/perf/imc-pmu.c

@@ -51,7 +51,7 @@ static int trace_imc_mem_size;
  * core and trace-imc
  */
 static struct imc_pmu_ref imc_global_refc = {
-	.lock = __SPIN_LOCK_INITIALIZER(imc_global_refc.lock),
+	.lock = __SPIN_LOCK_UNLOCKED(imc_global_refc.lock),
 	.id = 0,
 	.refc = 0,
 };