clocksource/drivers/clps711x: Remove board support

Since board support for the CLPS711X platform was removed,
remove the board support from the clps711x-timer driver.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lkml.kernel.org/r/20181220111626.17140-1-shc_work@mail.ru