[ARM] 4235/1: ns9xxx: declare the clock functions as "const"

This patch removes some "const"s that I introduced thinking they mean
the same thing as the "const"s introduced here.  So it fixes three warnings.

Signed-off-by: Uwe Kleine-König <ukleinek@informatik.uni-freiburg.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>