s390/vmcp: use page_to_virt instead of page_to_phys

Fix wrong usage of page_to_phys/phys_to_page.

Note: this currently doesn't fix a real bug, since virtual addresses
are indentical to physical ones.

Acked-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

drivers/s390/char/vmcp.c

@@ -72,7 +72,7 @@ static void vmcp_response_alloc(struct vmcp_session *session)
 	if (order > 2)
 		page = cma_alloc(vmcp_cma, nr_pages, 0, false);
 	if (page) {
-		session->response = (char *)page_to_phys(page);
+		session->response = (char *)page_to_virt(page);
 		session->cma_alloc = 1;
 		return;
 	}
@@ -89,7 +89,7 @@ static void vmcp_response_free(struct vmcp_session *session)
 	order = get_order(session->bufsize);
 	nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT;
 	if (session->cma_alloc) {
-		page = phys_to_page((unsigned long)session->response);
+		page = virt_to_page((unsigned long)session->response);
 		cma_release(vmcp_cma, page, nr_pages);
 		session->cma_alloc = 0;
 	} else {