util/amdfwtool: Allow 0-length blobs

A side effect of the change 8e0dca05
"util/amdfwtool: Add generic image copy function"
was to treat a read operation of zero bytes as a failure.  Some
implementations exist that use zero length files as a means of
removing functionality.  This causes amdfwtool to exit with an
error.

Put the zero length capability back in, and generate the requested
table entry with a length field of 0x0.

TEST=Boot google/grunt, inspect PSP directory table
BUG=b:128507639

Change-Id: Ifc9204dbbf6b107f06116362358ab9d22caa71df
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31891
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

0 files changed, 0 insertions, 0 deletions