staging: ion: remove dead code

ion_heap_pages_zero() function is not used at all, so remove it to
simplify the ion_heap_sglist_zero() function later.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20200619103636.11974-30-m.szyprowski@samsung.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion.h

@@ -177,7 +177,6 @@ void ion_heap_unmap_kernel(struct ion_heap *heap, struct ion_buffer *buffer);
 int ion_heap_map_user(struct ion_heap *heap, struct ion_buffer *buffer,
 		      struct vm_area_struct *vma);
 int ion_heap_buffer_zero(struct ion_buffer *buffer);
-int ion_heap_pages_zero(struct page *page, size_t size, pgprot_t pgprot);
 
 /**
  * ion_heap_init_shrinker

drivers/staging/android/ion/ion_heap.c

@@ -145,15 +145,6 @@ int ion_heap_buffer_zero(struct ion_buffer *buffer)
 	return ion_heap_sglist_zero(table->sgl, table->nents, pgprot);
 }
 
-int ion_heap_pages_zero(struct page *page, size_t size, pgprot_t pgprot)
-{
-	struct scatterlist sg;
-
-	sg_init_table(&sg, 1);
-	sg_set_page(&sg, page, size, 0);
-	return ion_heap_sglist_zero(&sg, 1, pgprot);
-}
-
 void ion_heap_freelist_add(struct ion_heap *heap, struct ion_buffer *buffer)
 {
 	spin_lock(&heap->free_lock);