eCryptfs: Remove buggy and unnecessary write in file name decode routine

Dmitry Chernenkov used KASAN to discover that eCryptfs writes past the
end of the allocated buffer during encrypted filename decoding. This
fix corrects the issue by getting rid of the unnecessary 0 write when
the current bit offset is 2.

Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Reported-by: Dmitry Chernenkov <dmitryc@google.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org # v2.6.29+: 51ca58dc eCryptfs: Filename Encryption: Encoding and encryption functions
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Git-commit: 942080643bce061c3dd9d5718d3b745dcb39a8bc
Git-repo: https://github.com/torvalds/linux.git


Change-Id: Ibf829d0a98a48163ee8bfb89e9951cd517352e25
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>