mm: cma: fix incorrect type conversion for size during dma allocation

This was found during userspace fuzzing test when a large size dma cma
allocation is made by driver(like ion) through userspace.

  show_stack+0x10/0x1c
  dump_stack+0x74/0xc8
  kasan_report_error+0x2b0/0x408
  kasan_report+0x34/0x40
  __asan_storeN+0x15c/0x168
  memset+0x20/0x44
  __dma_alloc_coherent+0x114/0x18c

Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/cma.h b/include/linux/cma.h
index f7ef093..29f9e77 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h
@@ -26,6 +26,6 @@
 extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
 					unsigned int order_per_bit,
 					struct cma **res_cma);
-extern struct page *cma_alloc(struct cma *cma, unsigned int count, unsigned int align);
+extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align);
 extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count);
 #endif