soc/intel/common/xhci: Fix building for 64bit

Tested with clang on prodrive/hermes: Boots to payload

Change-Id: I66392bcb4ed94c97dde43342dd29dab15d1dd9ea
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69234
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/intel/common/block/xhci/xhci.c b/src/soc/intel/common/block/xhci/xhci.c
index 4a40834..a12f875 100644
--- a/src/soc/intel/common/block/xhci/xhci.c
+++ b/src/soc/intel/common/block/xhci/xhci.c
@@ -27,7 +27,7 @@
 	if (mem_base == 0 || mem_base == 0xffffffff)
 		return 0;
 
-	return (uint8_t *)(mem_base & ~PCI_BASE_ADDRESS_MEM_ATTR_MASK);
+	return (uint8_t *)(uintptr_t)(mem_base & ~PCI_BASE_ADDRESS_MEM_ATTR_MASK);
 }
 
 void xhci_host_reset(void)