Simplify constant-time RSA padding check.

(Imported form upstream's 455b65dfab0de51c9f67b3c909311770f2b3f801 and
0d6a11a91f4de238ce533c40bd9507fe5d95f288)

Change-Id: Ia195c7fe753cfa3a7f8c91d2d7b2cd40a547be43
2 files changed