staging: gasket: Convert get_user_pages*() --> pin_user_pages*()

In 2019, we introduced pin_user_pages*() and now we are converting
get_user_pages*() to the new API as appropriate. [1] & [2] could
be referred for more information.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
	https://lwn.net/Articles/807108/Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>

Link: https://lore.kernel.org/r/1592361930-3813-1-git-send-email-jrdr.linux@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/gasket/gasket_page_table.c

@@ -449,7 +449,7 @@ static bool gasket_release_page(struct page *page)
 
 	if (!PageReserved(page))
 		SetPageDirty(page);
-	put_page(page);
+	unpin_user_page(page);
 
 	return true;
 }
@@ -486,12 +486,12 @@ static int gasket_perform_mapping(struct gasket_page_table *pg_tbl,
 			ptes[i].dma_addr = pg_tbl->coherent_pages[0].paddr +
 					   off + i * PAGE_SIZE;
 		} else {
-			ret = get_user_pages_fast(page_addr - offset, 1,
+			ret = pin_user_pages_fast(page_addr - offset, 1,
 						  FOLL_WRITE, &page);
 
 			if (ret <= 0) {
 				dev_err(pg_tbl->device,
-					"get user pages failed for addr=0x%lx, offset=0x%lx [ret=%d]\n",
+					"pin user pages failed for addr=0x%lx, offset=0x%lx [ret=%d]\n",
 					page_addr, offset, ret);
 				return ret ? ret : -ENOMEM;
 			}