tgsi/scan: add info about declared samplers (v2)

v2: get it from declarations, not instructions

src/gallium/auxiliary/tgsi/tgsi_scan.c

@@ -409,6 +409,8 @@ tgsi_scan_shader(const struct tgsi_token *tokens,
                         info->writes_edgeflag = TRUE;
                      }
                   }
+               } else if (file == TGSI_FILE_SAMPLER) {
+                  info->samplers_declared |= 1 << reg;
                }
             }
          }

src/gallium/auxiliary/tgsi/tgsi_scan.h

@@ -64,6 +64,7 @@ struct tgsi_shader_info
    uint file_count[TGSI_FILE_COUNT];  /**< number of declared registers */
    int file_max[TGSI_FILE_COUNT];  /**< highest index of declared registers */
    int const_file_max[PIPE_MAX_CONSTANT_BUFFERS];
+   unsigned samplers_declared; /**< bitmask of declared samplers */
 
    ubyte input_array_first[PIPE_MAX_SHADER_INPUTS];
    ubyte input_array_last[PIPE_MAX_SHADER_INPUTS];