dca: fixup initialization dependency

commit 1207e795568a368928dfd23d6817e47f2e8097e3 upstream

Mark dca_init as a subsys_initcall since it needs to be ready to go
before dependent drivers start registering themselves.

Reported-and-tested-by: Mark Rustad <mark_rustad@Xiotech.com>
Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>