UBIFS: fix warning: format '%lX' expects type 'long unsigned int'

Commit 46d7274c "UBIFS: Change ubifsload to set the filesize variable"
introduced the follwing compiler warning:

ubifs.c: In function 'ubifs_load':
ubifs.c:742: warning: format '%lX' expects type 'long unsigned int', but argument 3 has type 'u32'
Signed-off-by: NWolfgang Denk <wd@denx.de>
Cc: Bastian Ruppert <Bastian.Ruppert@Sewerin.de>

fs/ubifs/ubifs.c

@@ -739,7 +739,7 @@ int ubifs_load(char *filename, u32 addr, u32 size)
 	if (err)
 		printf("Error reading file '%s'\n", filename);
 	else {
-	        sprintf(buf, "%lX", size);
+	        sprintf(buf, "%X", size);
 		setenv("filesize", buf);
 		printf("Done\n");
 	}