Remove CONFIG_CONSISTENT_RECODE flag

Remove CONFIG_CONSISTENT_RECODE flag

Currently, libvpx does not properly clear and re-initialize the memories
when it re-encodes a frame. As a result, out-of-date values are used in
the encoding process, and re-encoding a frame with the same parameter
will give different outputs.

This commit enables the code under CONFIG_CONSISTENT_RECODE to correct
this behavior. This change has minor effect on the coding performance,
but it ensures valid values are used in the encoding process.

Furthermore, the flag is removed as it is now always turned on.

Performance:
| SPD_SET | TESTSET | AVG_PSNR | OVR_PSNR |  SSIM   | ENC_T |
|---------|---------|----------|----------|---------|-------|
|    0    | hdres2  | -0.012%  | -0.021%  | -0.030% | +0.1% |
|    0    | lowres2 | +0.029%  | +0.019%  | +0.047% | +0.1% |
|    0    | midres2 | -0.004%  | +0.009%  | +0.026% | +0.1% |
|---------|---------|----------|----------|---------|-------|
|    1    | hdres2  | +0.032%  | +0.032%  | -0.000% | -0.0% |
|    1    | lowres2 | -0.005%  | -0.011%  | -0.014% | +0.0% |
|    1    | midres2 | +0.004%  | +0.020%  | +0.027% | +0.2% |
|---------|---------|----------|----------|---------|-------|
|    2    | hdres2  | +0.048%  | +0.056%  | +0.057% | +0.1% |
|    2    | lowres2 | +0.007%  | +0.002%  | -0.016% | -0.0% |
|    2    | midres2 | -0.015%  | -0.008%  | -0.002% | +0.1% |
|---------|---------|----------|----------|---------|-------|
|    3    | hdres2  | +0.010%  | +0.014%  | +0.004% | -0.0% |
|    3    | lowres2 | +0.000%  | -0.021%  | -0.001% | +0.0% |
|    3    | midres2 | +0.007%  | -0.038%  | +0.012% | -0.2% |
|---------|---------|----------|----------|---------|-------|
|    4    | hdres2  | +0.107%  | +0.136%  | +0.124% | -0.0% |
|    4    | lowres2 | -0.012%  | -0.024%  | -0.020% | -0.0% |
|    4    | midres2 | +0.055%  | -0.004%  | +0.048% | -0.1% |
|---------|---------|----------|----------|---------|-------|
|    5    | hdres2  | +0.026%  | +0.027%  | +0.020% | -0.0% |
|    5    | lowres2 | +0.009%  | -0.008%  | +0.028% | +0.1% |
|    5    | midres2 | -0.025%  | +0.021%  | -0.020% | -0.1% |

STATS_CHANGED

Change-Id: I3967aee8c8e4d0608a492e07f99ab8de9744ba57