saa7134-alsa: include vmalloc.h

Changeset 15e64f0d broke compilation on several archs, as it
forgot to include vmalloc.h.

drivers/media/pci/saa7134/saa7134-alsa.c: In function ‘saa7134_alsa_dma_init’:
  CC [M]  drivers/media/rc/keymaps/rc-behold-columbus.o
drivers/media/pci/saa7134/saa7134-alsa.c:283:2: error: implicit declaration of function ‘vmalloc_32’ [-Werror=implicit-function-declaration]
  dma->vaddr = vmalloc_32(nr_pages << PAGE_SHIFT);
  ^
drivers/media/pci/saa7134/saa7134-alsa.c:283:13: warning: assignment makes pointer from integer without a cast [enabled by default]
  dma->vaddr = vmalloc_32(nr_pages << PAGE_SHIFT);
             ^
drivers/media/pci/saa7134/saa7134-alsa.c:296:2: error: implicit declaration of function ‘vzalloc’ [-Werror=implicit-function-declaration]
  dma->sglist = vzalloc(dma->nr_pages * sizeof(*dma->sglist));
  ^
drivers/media/pci/saa7134/saa7134-alsa.c:296:14: warning: assignment makes pointer from integer without a cast [enabled by default]
  dma->sglist = vzalloc(dma->nr_pages * sizeof(*dma->sglist));
              ^
drivers/media/pci/saa7134/saa7134-alsa.c:310:2: error: implicit declaration of function ‘vfree’ [-Werror=implicit-function-declaration]
  vfree(dma->sglist);

Add it to avoid such breakages.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>