nvdimm: Remove duplicate linux/slab.h header

./drivers/nvdimm/bus.c: linux/slab.h is included more than once.

Reported-by: Abaci Robot <[email protected]>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=25516
Signed-off-by: Jiapeng Chong <[email protected]>
Signed-off-by: Ira Weiny <[email protected]>

Author: Jiapeng Chong

drivers/nvdimm/bus.c

@@ -13,7 +13,6 @@
 #include <linux/async.h>
 #include <linux/ndctl.h>
 #include <linux/sched.h>
-#include <linux/slab.h>
 #include <linux/cpu.h>
 #include <linux/fs.h>
 #include <linux/io.h>