parisc/power: Move soft-power into power.c

Move the soft-power ctl table into parisc/power.c. As a consequence the
pwrsw_enabled var is made static.

This is part of a greater effort to move ctl tables into their
respective subsystems which will reduce the merge conflicts in
kernel/sysctl.c.

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Joel Granados <joel.granados@kernel.org>

include/linux/sysctl.h

@@ -242,7 +242,6 @@ int do_proc_douintvec(const struct ctl_table *table, int write,
 				  int write, void *data),
 		      void *data);
 
-extern int pwrsw_enabled;
 extern int unaligned_enabled;
 extern int unaligned_dump_stack;
 extern int no_unaligned_warning;