cpuidle: Fix cpuidle_remove_state_sysfs() kerneldoc comment

Fix function name in sysfs.c kernel-doc comment
to remove a warning found by running scripts/kernel-doc,
which is caused by using 'make W=1'.

drivers/cpuidle/sysfs.c:512: warning: expecting prototype for
cpuidle_remove_driver_sysfs(). Prototype was for
cpuidle_remove_state_sysfs() instead

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
[ rjw: Subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>