clocksource: Fix Kconfig miscues

Fix lots of typo, spelling, punctuation, and grammar miscues in
drivers/clocksource/Kconfig.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/4deb42a9-82f2-72f9-891f-972a9a399f4f@infradead.org