cr50_fuzz: Fix broken compilation
cr50_fuzz: Fix broken compilation

Adds mock implementation of get_current_pcr_digest() for the fuzz
target.

BRANCH=None
BUG=chromium:903487
TEST=make -j buildfuzztests

Change-Id: I55b7da813d4f17ef7f60e045423a3917a052e41c
Signed-off-by: Allen Webb <880184b418addffb87cd9c8e8e882ca6764ac96b@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/1327128
Reviewed-by: Manoj Gupta <1d49d0f302d724a1dc5fc4d717d15418e9808ddd@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec