Silence label without a colon warning with nasm.

Change-Id: Idf32db95ad25747cd6fa6fc2803b012e7994cf3c

av1/encoder/x86/temporal_filter_apply_sse2.asm

diff --git a/av1/encoder/x86/temporal_filter_apply_sse2.asm b/av1/encoder/x86/temporal_filter_apply_sse2.asm
index c88312e..7186b6b 100644
--- a/av1/encoder/x86/temporal_filter_apply_sse2.asm
+++ b/av1/encoder/x86/temporal_filter_apply_sse2.asm
@@ -211,5 +211,5 @@
 _const_top_bit:
     times 8 dw 1<<15
 align 16
-_const_16w
+_const_16w:
     times 8 dw 16