Replace "colorspace" with "color_space"

This is to make the usage of the variable name consistent across
the code base.

Change-Id: I698739e55841c59358d1c6e5cc97c96088772943

vp9/vp9_dx_iface.c

diff --git a/vp9/vp9_dx_iface.c b/vp9/vp9_dx_iface.c
index b917787..c0e4297 100644
--- a/vp9/vp9_dx_iface.c
+++ b/vp9/vp9_dx_iface.c
@@ -95,12 +95,11 @@
 
 static int parse_bitdepth_colorspace_sampling(
     BITSTREAM_PROFILE profile, struct vp9_read_bit_buffer *rb) {
-  const int sRGB = 7;
-  int colorspace;
+  vpx_color_space_t color_space;
   if (profile >= PROFILE_2)
     rb->bit_offset += 1;  // Bit-depth 10 or 12.
-  colorspace = vp9_rb_read_literal(rb, 3);
-  if (colorspace != sRGB) {
+  color_space = (vpx_color_space_t)vp9_rb_read_literal(rb, 3);
+  if (color_space != VPX_CS_SRGB) {
     rb->bit_offset += 1;  // [16,235] (including xvycc) vs [0,255] range.
     if (profile == PROFILE_1 || profile == PROFILE_3) {
       rb->bit_offset += 2;  // subsampling x/y.