clocksource/drivers/arm_global_timer: Fix maximum prescaler value

The prescaler in the "Global Timer Control Register bit assignments" is
documented to use bits [15:8], which means that the maximum prescaler
register value is 0xff.

Fixes: 171b45a ("clocksource/drivers/arm_global_timer: Implement rate compensation whenever source clock changes")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20240218174138.1942418-2-martin.blumenstingl@googlemail.com

Author: xdarklight

drivers/clocksource/arm_global_timer.c

@@ -32,7 +32,7 @@
 #define GT_CONTROL_IRQ_ENABLE		BIT(2)	/* banked */
 #define GT_CONTROL_AUTO_INC		BIT(3)	/* banked */
 #define GT_CONTROL_PRESCALER_SHIFT      8
-#define GT_CONTROL_PRESCALER_MAX        0xF
+#define GT_CONTROL_PRESCALER_MAX        0xFF
 #define GT_CONTROL_PRESCALER_MASK       (GT_CONTROL_PRESCALER_MAX << \
 					 GT_CONTROL_PRESCALER_SHIFT)