[PATCH] drivers/base - fix sparse warnings

There are a number of sparse warnings from the latest sparse
snapshot being generated from the drivers/base build. The
main culprits are due to the initialisation functions not
being declared in a header file.

Also, the firmware.c file should include <linux/device.h>
to get the prototype of  firmware_register() and
firmware_unregister().

This patch moves the init function declerations from the
init.c file to the base.h, and ensures it is included in
all the relevant c sources. It also adds <linux/device.h>
to the included headers for firmware.c.

The patch does not solve all the sparse errors generated,
but reduces the count significantly.

drivers/base/core.c:161:1: warning: symbol 'devices_subsys' was not declared. Should it be static?
drivers/base/core.c:417:12: warning: symbol 'devices_init' was not declared. Should it be static?
drivers/base/sys.c:253:6: warning: symbol 'sysdev_shutdown' was not declared. Should it be static?
drivers/base/sys.c:326:5: warn...