staging: comedi: Add missing #include <linux/slab.h>

staging: comedi: Add missing #include <linux/slab.h>

sparc64 allmodconfig:

drivers/staging/comedi/drivers/addi_apci_2032.c: In function 'apci2032_auto_attach':
drivers/staging/comedi/drivers/addi_apci_2032.c:328:3: error: implicit declaration of function 'kzalloc' [-Werror=implicit-function-declaration]
drivers/staging/comedi/drivers/addi_apci_2032.c:328:11: warning: assignment makes pointer from integer without a cast [enabled by default]
drivers/staging/comedi/drivers/addi_apci_2032.c: In function 'apci2032_detach':
drivers/staging/comedi/drivers/addi_apci_2032.c:350:3: error: implicit declaration of function 'kfree' [-Werror=implicit-function-declaration]

drivers/staging/comedi/drivers/amplc_pci224.c: In function 'pci224_attach_common':
drivers/staging/comedi/drivers/amplc_pci224.c:1289:2: error: implicit declaration of function 'kmalloc' [-Werror=implicit-function-declaration]
drivers/staging/comedi/drivers/amplc_pci224.c:1289:23: warning: assignment makes pointer from integer without a cast [enabled by default]
drivers/staging/comedi/drivers/amplc_pci224.c:1296:24: warning: assignment makes pointer from integer without a cast [enabled by default]
drivers/staging/comedi/drivers/amplc_pci224.c:1303:25: warning: assignment makes pointer from integer without a cast [enabled by default]
drivers/staging/comedi/drivers/amplc_pci224.c:1348:42: warning: assignment makes pointer from integer without a cast [enabled by default]
drivers/staging/comedi/drivers/amplc_pci224.c: In function 'pci224_detach':
drivers/staging/comedi/drivers/amplc_pci224.c:1474:3: error: implicit declaration of function 'kfree' [-Werror=implicit-function-declaration]

Introduced by commit 0bdab509bf9c6d838dc0a3b1d68bbf841fc20b5a ("staging:
comedi: use comedi_alloc_devpriv()"), which removed some inclusions of
<linux/slab.h>.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>