Daala TX does not scale coefficients based on TX size.  Although
previous patches force av1_get_tx_scale() to always return zero when
CONFIG_DAALA_TX is true, this patch removes the call entirely.  This
represents no functional change.

subset-1:
monty-rest-of-stack-Q3-s1@2017-11-13T14:39:52.160Z ->
 monty-rest-of-stack-rmscale-s1@2017-11-13T14:40:20.646Z

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |   SSIM | MS SSIM | CIEDE 2000
0.0000 |     N/A |  0.0000 |   0.0000 | 0.0000 |  0.0000 |     0.0000

Change-Id: I5757282153c291c59510b17b5f71b3e0a56382ca