clocksource/drivers/exynos_mct: Rename Exynos to lowercase

Fix up inconsistent usage of upper and lowercase letters in "Exynos"
name.

"EXYNOS" is not an abbreviation but a regular trademarked name.
Therefore it should be written with lowercase letters starting with
capital letter.

The lowercase "Exynos" name is promoted by its manufacturer Samsung
Electronics Co., Ltd., in advertisement materials and on website.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200104152107.11407-12-krzk@kernel.org

drivers/clocksource/exynos_mct.c

@@ -4,7 +4,7 @@
  * Copyright (c) 2011 Samsung Electronics Co., Ltd.
  *		http://www.samsung.com
  *
- * EXYNOS4 MCT(Multi-Core Timer) support
+ * Exynos4 MCT(Multi-Core Timer) support
 */
 
 #include <linux/interrupt.h>