bios_emulator: Fix cast for 64-bit compilation

Fix a cast that causes warnings on 64-bit machines.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

drivers/bios_emulator/atibios.c

@@ -599,7 +599,7 @@ int biosemu_run(pci_dev_t pcidev, uchar *bios_rom, int bios_len,
 	if (clean_up) {
 		BE_exit();
 		if (vga_info->BIOSImage &&
-		    (u32)(vga_info->BIOSImage) != 0xc0000)
+		    (ulong)(vga_info->BIOSImage) != 0xc0000)
 			free(vga_info->BIOSImage);
 		free(vga_info);
 		vga_info = NULL;