Driver core: fix devres_release_all() return value

Every file should include the headers containing the prototypes for
it's global functions.

Since the GNU C compiler is now able to detect that the function 
prototype of devres_release_all() in the header and the actual function 
disagree regarding the return value, this patch also fixes this bug.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>