s9036: Fix [-Wshift-negative-value] compiler warning

backend/s9036.c

@@ -654,9 +654,9 @@ init_options (S9036_Scanner * s)
 
   static const SANE_Range percentage_range =
   {
-    -100 << SANE_FIXED_SCALE_SHIFT,	/* minimum */
-    100 << SANE_FIXED_SCALE_SHIFT,	/* maximum */
-    1 << SANE_FIXED_SCALE_SHIFT	/* quantization */
+    SANE_FIX(-100),	/* minimum */
+    SANE_FIX(100),	/* maximum */
+    SANE_FIX(1)         /* quantization */
   };
 
   static const SANE_Range automatic_adjust_range =