driver core: fix build with SYSFS=n

When SYSFS=n and MODULES=y, build ends with:

linux-2.6.24-rc6-mm1/drivers/base/module.c: In function 'module_add_driver':
linux-2.6.24-rc6-mm1/drivers/base/module.c:49: error: 'module_kset' undeclared (first use in this function)
make[3]: *** [drivers/base/module.o] Error 1

Below is one possible fix.
Build-tested with all 4 config combinations of SYSFS & MODULES.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index ff26968..63e09c0 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -11,7 +11,9 @@
 obj-$(CONFIG_NUMA)	+= node.o
 obj-$(CONFIG_MEMORY_HOTPLUG_SPARSE) += memory.o
 obj-$(CONFIG_SMP)	+= topology.o
+ifeq ($(CONFIG_SYSFS),y)
 obj-$(CONFIG_MODULES)	+= module.o
+endif
 obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
 
 ifeq ($(CONFIG_DEBUG_DRIVER),y)