verity: define NR_CPUS

Needed by dm-bht.h in a future (next) CL.

BUG=chromium-os:9752
TEST=Ran unit tests from dm-verity.git.

Change-Id: Ic57de2ec28d303ad2356dc504278abbcda29b984
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Reviewed-on: http://gerrit.chromium.org/gerrit/6784
Reviewed-by: Will Drewry <wad@chromium.org>
1 file changed