This is entirely unnecessary (we can ask the signer backend to export the
key to a file when needed), and was causing confusing selftest failures
due to the variable being set from two different places.
[YOCTO #11191]
(From OE-Core rev: 74ea979044368dc28c24325e7e77471b70aa8fe8)
Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>