csky: Fixup csky_pmu.max_period assignment

The csky_pmu.max_period has type u64, and BIT() can only return
32 bits unsigned long on C-SKY. The initialization for max_period
will be incorrect when count_width is bigger than 32.

Use BIT_ULL()

Signed-off-by: Mao Han <han_mao@c-sky.com>
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
diff --git a/arch/csky/kernel/perf_event.c b/arch/csky/kernel/perf_event.c
index 4c1a193..7570109 100644
--- a/arch/csky/kernel/perf_event.c
+++ b/arch/csky/kernel/perf_event.c
@@ -1306,7 +1306,7 @@
 				 &csky_pmu.count_width)) {
 		csky_pmu.count_width = DEFAULT_COUNT_WIDTH;
 	}
-	csky_pmu.max_period = BIT(csky_pmu.count_width) - 1;
+	csky_pmu.max_period = BIT_ULL(csky_pmu.count_width) - 1;
 
 	csky_pmu.plat_device = pdev;