gve: fix -ENOMEM null check on a page allocation

Currently the check to see if a page is allocated is incorrect
and is checking if the pointer page is null, not *page as
intended.  Fix this.

Addresses-Coverity: ("Dereference before null check")
Fixes: f5cedc84 ("gve: Add transmit and receive support")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/google/gve/gve_main.c

@@ -518,7 +518,7 @@ int gve_alloc_page(struct device *dev, struct page **page, dma_addr_t *dma,
 		   enum dma_data_direction dir)
 {
 	*page = alloc_page(GFP_KERNEL);
-	if (!page)
+	if (!*page)
 		return -ENOMEM;
 	*dma = dma_map_page(dev, *page, 0, PAGE_SIZE, dir);
 	if (dma_mapping_error(dev, *dma)) {