x86: Correct missing local variable in bootm

Enabling FIT produces a compile error. Fix this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/lib/bootm.c b/arch/x86/lib/bootm.c
index 2520228..0d3250c 100644
--- a/arch/x86/lib/bootm.c
+++ b/arch/x86/lib/bootm.c
@@ -63,6 +63,8 @@
 		}
 #if defined(CONFIG_FIT)
 	} else if (images->fit_uname_os) {
+		int ret;
+
 		ret = fit_image_get_data(images->fit_hdr_os,
 					images->fit_noffset_os, &data, &len);
 		if (ret) {