Because daala_tx only ever does an unbiased shift by 1, we can replace
 the varible shift macro with a simpler hardcoded implementation.
This patch causes no change in behavior.

subset-1:

daala_tx@2017-11-04T07:20:17.571Z ->
 daala_tx-no_op@2017-11-04T07:21:06.231Z

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |   SSIM | MS SSIM | CIEDE 2000
0.0000 |  0.0000 |  0.0000 |   0.0000 | 0.0000 |  0.0000 |     0.0000

Change-Id: Ifddfef079320de0df09d9bc39757af9fe81e3c38