libpayload: Fix pointer related casts

Fix pointer related casts since this can create a problem for 64-bit systems.

BUG=None
BRANCH=None
TEST=Compiled successfully for link, nyan using emerge-* libpayload

Original-Change-Id: I4cbd2d9f1efaaac87c3eba69204337fd6893ed66
Original-Reviewed-on: https://chromium-review.googlesource.com/199564
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Original-Commit-Queue: Furquan Shaikh <furquan@chromium.org>
Original-Tested-by: Furquan Shaikh <furquan@chromium.org>
(cherry picked from commit 914b118a64b0691aeca463dff24252db9c24109e)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I11f070ed5d3eddd8b9be30c428cb24c8439e617b
Reviewed-on: http://review.coreboot.org/7905
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)
diff --git a/payloads/libpayload/drivers/usb/xhci.c b/payloads/libpayload/drivers/usb/xhci.c
index 714c9ce..33009bc 100644
--- a/payloads/libpayload/drivers/usb/xhci.c
+++ b/payloads/libpayload/drivers/usb/xhci.c
@@ -168,7 +168,7 @@
 	controller->poll_intr_queue	= xhci_poll_intr_queue;
 	controller->pcidev		= 0;
 
-	controller->reg_base = (u32)physical_bar;
+	controller->reg_base = (uintptr_t)physical_bar;
 	controller->instance = xzalloc(sizeof(xhci_t));
 	xhci_t *const xhci = (xhci_t *)controller->instance;