utk: building ExtHeader erase polarity not 0x00 or 0xFF, got 0xf0

[xaionaro]

Hello. It looks like verb create-fv does not work in the utk tool on an empty image:

xaionaro@void:~/go/src/github.com/linuxboot/fiano$ dd if=/dev/zero of=/tmp/image bs=1K count=64
64+0 records in
64+0 records out
65536 bytes (66 kB, 64 KiB) copied, 0.00071909 s, 91.1 MB/s
xaionaro@void:~/go/src/github.com/linuxboot/fiano$ go run ./cmds/utk/ /tmp/image create-fv $((32 * 1024)) $((32 * 1024 - 16)) "61C0F511-A691-4F54-974F-B9A42172CE53"
2022/01/17 19:41:14 [fiano][FATAL] building ExtHeader erase polarity not 0x00 or 0xFF, got 0xf0
exit status 1

[xaionaro]

Created a PR to workaround the problem.