sysdev: the cpu probe/release attributes should be sysdev_class_attributes

This fixes these warnings:

drivers/base/cpu.c:264: warning: initialization from incompatible pointer type
drivers/base/cpu.c:265: warning: initialization from incompatible pointer type

Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>