mmc: core: Exclude unnecessary header file

From the 4.19 kernel, thread related code has been removed in queue.c.
So we can exclude unnecessary header file.
Signed-off-by: NChanWoo Lee <cw9316.lee@samsung.com>
Acked-by: NColy Li <colyli@suse.de>
Link: https://lore.kernel.org/r/20210125064355.28545-1-cw9316.lee@samsung.comSigned-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/queue.c

@@ -7,7 +7,6 @@
 #include <linux/module.h>
 #include <linux/blkdev.h>
 #include <linux/freezer.h>
-#include <linux/kthread.h>
 #include <linux/scatterlist.h>
 #include <linux/dma-mapping.h>
 #include <linux/backing-dev.h>