fastboot: fix arg handling causing no-op.

Change-Id: I89d4a6d14e542d8f2d7832d94b0a7cee6eb88305
diff --git a/fastboot/fastboot.c b/fastboot/fastboot.c
index e79e6c2..2ddc4f8 100644
--- a/fastboot/fastboot.c
+++ b/fastboot/fastboot.c
@@ -525,7 +525,7 @@
 }
 
 #define skip(n) do { argc -= (n); argv += (n); } while (0)
-#define require(n) do { if (argc < (n)) usage(); exit(1);} while (0)
+#define require(n) do { if (argc < (n)) {usage(); exit(1);}} while (0)
 
 int do_oem_command(int argc, char **argv)
 {