mlxsw: core_linecards: Remove duplicated include in core_linecard_dev.c

Fix following includecheck warning:
./drivers/net/ethernet/mellanox/mlxsw/core_linecard_dev.c: linux/err.h is included more than once.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/20220727233801.23781-1-yang.lee@linux.alibaba.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlxsw/core_linecard_dev.c

@@ -5,7 +5,6 @@
 #include <linux/module.h>
 #include <linux/err.h>
 #include <linux/types.h>
-#include <linux/err.h>
 #include <linux/auxiliary_bus.h>
 #include <linux/idr.h>
 #include <linux/gfp.h>