gallium/tgsi: Define the TGSI_BUFFER texture target.

This texture type was already referred to by the documentation but it
was never defined.  Define it as 0 to match the pipe_texture_target
enumeration values.

src/gallium/auxiliary/tgsi/tgsi_build.c

@@ -709,7 +709,7 @@ tgsi_default_instruction_texture( void )
 {
    struct tgsi_instruction_texture instruction_texture;
 
-   instruction_texture.Texture = TGSI_TEXTURE_UNKNOWN;
+   instruction_texture.Texture = TGSI_BUFFER;
    instruction_texture.NumOffsets = 0;
    instruction_texture.Padding = 0;
 

src/gallium/auxiliary/tgsi/tgsi_strings.c

@@ -79,7 +79,7 @@ const char *tgsi_semantic_names[TGSI_SEMANTIC_COUNT] =
 
 const char *tgsi_texture_names[TGSI_TEXTURE_COUNT] =
 {
-   "UNKNOWN",
+   "BUFFER",
    "1D",
    "2D",
    "3D",

src/gallium/auxiliary/util/u_blitter.c

@@ -674,7 +674,7 @@ pipe_tex_to_tgsi_tex(enum pipe_texture_target pipe_tex_target)
       return TGSI_TEXTURE_2D_ARRAY;
    default:
       assert(0 && "unexpected texture target");
-      return TGSI_TEXTURE_UNKNOWN;
+      return 0;
    }
 }
 

src/gallium/drivers/nv50/codegen/nv50_ir_from_tgsi.cpp

@@ -347,8 +347,8 @@ static nv50_ir::TexTarget translateTexture(uint tex)
    NV50_IR_TEX_TARG_CASE(SHADOW2D_ARRAY, 2D_ARRAY_SHADOW);
    NV50_IR_TEX_TARG_CASE(SHADOWCUBE, CUBE_SHADOW);
    NV50_IR_TEX_TARG_CASE(SHADOWRECT, RECT_SHADOW);
-
-   case TGSI_TEXTURE_UNKNOWN:
+   case TGSI_BUFFER:
+      return nv50_ir::TEX_TARGET_BUFFER;
    default:
       assert(!"invalid texture target");
       return nv50_ir::TEX_TARGET_2D;

src/gallium/include/pipe/p_shader_tokens.h

@@ -466,7 +466,7 @@ struct tgsi_instruction_label
    unsigned Padding  : 8;
 };
 
-#define TGSI_TEXTURE_UNKNOWN        0
+#define TGSI_BUFFER                 0
 #define TGSI_TEXTURE_1D             1
 #define TGSI_TEXTURE_2D             2
 #define TGSI_TEXTURE_3D             3