gve: fix dma sync bug where not all pages synced

The previous commit had a bug where the last page in the memory range
could not be synced. This change fixes the behavior so that all the
required pages are synced.

Fixes: 9cfeeb576d49 ("gve: Fixes DMA synchronization")
Signed-off-by: Adi Suresh <[e-mail]>
Reviewed-by: Catherine Sullivan <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

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

···
 static void gve_dma_sync_for_device(struct device *dev, dma_addr_t *page_buses,
 				    u64 iov_offset, u64 iov_len)
 {
+	u64 last_page = (iov_offset + iov_len - 1) / PAGE_SIZE;
+	u64 first_page = iov_offset / PAGE_SIZE;
 	dma_addr_t dma;
-	u64 addr;
+	u64 page;
 
-	for (addr = iov_offset; addr < iov_offset + iov_len;
-	     addr += PAGE_SIZE) {
-		dma = page_buses[addr / PAGE_SIZE];
+	for (page = first_page; page <= last_page; page++) {
+		dma = page_buses[page];
 		dma_sync_single_for_device(dev, dma, PAGE_SIZE, DMA_TO_DEVICE);
 	}
 }