sandbox: Fix warning in display_options

This fixes a warning in the print_buffer() function with some toolchains.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/lib/display_options.c b/lib/display_options.c
index 24d8f55..57fb974 100644
--- a/lib/display_options.c
+++ b/lib/display_options.c
@@ -152,7 +152,7 @@
 			else
 				x = lb.uc[i] = *(volatile uint8_t *)data;
 #ifdef CONFIG_SYS_SUPPORT_64BIT_DATA
-			printf(" %0*" PRIx64, width * 2, x);
+			printf(" %0*llx", width * 2, (long long)x);
 #else
 			printf(" %0*x", width * 2, x);
 #endif