MIPS: Always register R4K clock when selected

Always register the R4K clocksource when CONFIG_CSRC_R4K is selected,
regardless of selected support for other clocksources. The kernel will
select the best clocksource based on their ratings, making it safe to
register R4K unconditionally and use it as a fallback should the
kernel be run on a system where other selected clocksources are
inoperable.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6024/


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