drivers/base/bus.c: local variables should not be exposed globally

The variable 'system_kset' is only referenced in this file and
should be marked static to prevent it from being exposed globally.

This quiets the sparse waring:

warning: symbol 'system_kset' was not declared. Should it be static?

Also, remove the comment since drivers/base/sys.c has now been
deleted.
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/bus.c

@@ -21,8 +21,7 @@
 #include "power/power.h"
 
 /* /sys/devices/system */
-/* FIXME: make static after drivers/base/sys.c is deleted */
-struct kset *system_kset;
+static struct kset *system_kset;
 
 #define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)