clocksource: arm_global_timer: fix non-kernel-doc comment

Use a common C comment "/*" instead of a kernel-doc marker "/**"
to prevent kernel-doc warnings:

arm_global_timer.c:92: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 * To ensure that updates to comparator value register do not set the
arm_global_timer.c:92: warning: missing initial short description on line:
 * To ensure that updates to comparator value register do not set the

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20240115053641.29129-1-rdunlap@infradead.org