Rename base/hash/sha1.cc to base/hash/sha1_nacl.cc.

Prior to implementing streaming SHA-1 algorithm, rename the file to
reflect that it's an implementation only used for NaCl.

BUG=1189711

Change-Id: I52055527f489016bb52d131b7fd8c3cd74bac89b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2775816


Auto-Submit: Alice Gong <alicego@google.com>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#864932}