blk_mq: linux/blk-mq.h does not include all the headers it depends on

and building block/blk-mq-pci.o should depend on CONFIG_BLOCK

Fixes: 973c4e372c8f ("blk-mq: provide a default queue mapping for PCI device")
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq-pci.c b/block/blk-mq-pci.c
index 33c7bd7..966c216 100644
--- a/block/blk-mq-pci.c
+++ b/block/blk-mq-pci.c
@@ -10,6 +10,8 @@
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  * more details.
  */
+#include <linux/kobject.h>
+#include <linux/blkdev.h>
 #include <linux/blk-mq.h>
 #include <linux/blk-mq-pci.h>
 #include <linux/pci.h>