serial: 8250_em: Drop unused header file

Drop unused header file slab.h from the driver.
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20230227114152.22265-4-biju.das.jz@bp.renesas.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_em.c

@@ -13,7 +13,6 @@
 #include <linux/serial_reg.h>
 #include <linux/platform_device.h>
 #include <linux/clk.h>
-#include <linux/slab.h>
 
 #include "8250.h"