MIPS: Lemote 2F: cs5536: mfgpt: depend on !highres

This timer does not support oneshot mode and as such the system remains
in periodic mode and won't support high res timers.
This patch adds a note about this in Kconfig and lets it depend on
!highres so users which want to use high timers don' stuck with this
timer.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-mips@linux-mips.org
Cc: Hua Yan <yanh@lemote.com>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Alex Smith <alex.smith@imgtec.com>
Cc: Hongliang Tao <taohl@lemote.com>
Cc: Wu Zhangjin <wuzhangjin@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/6935/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>