drm/nv98/crypt: fix fuc build with latest envyas

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/engine/crypt/fuc/nv98.fuc

@@ -238,7 +238,7 @@ ih:
 			cmpu b32 $r4 0x60+#dma_count
 			bra nc #illegal_mthd
 			shl b32 $r5 $r4 2
-			add b32 $r5 (#ctx_dma - 0x60 * 4) & 0xffff
+			add b32 $r5 ((#ctx_dma - 0x60 * 4) & 0xffff)
 			bset $r3 0x1e
 			st b32 D[$r5] $r3
 			add b32 $r4 0x180 - 0x60