libcr51sign: import from gBMC

Validate the cr51 descriptor of the BIOS image. It can also
parse the BIOS version and write it to a file.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I098be66b228da6f3514d3f13166a1bb4e1e718fb
diff --git a/subprojects/libcr51sign/OWNERS b/subprojects/libcr51sign/OWNERS
new file mode 100644
index 0000000..1dca102
--- /dev/null
+++ b/subprojects/libcr51sign/OWNERS
@@ -0,0 +1 @@
+nanzhoumails@gmail.com