amdfwtool: make fields unsigned

The value stored in `gen` is only ever `1` or `0`. Storing `1` causes
Clang to warn, since the only valid values for a 1-bit int are -1 and 0:
```
amdfwtool.c:1487:27: error: implicit truncation from 'int' to a one-bit
wide bit-field changes value from 1 to -1
[-Werror,-Wsingle-bit-bitfield-constant-conversion]
 1487 |                 amd_romsig->efs_gen.gen = EFS_BEFORE_SECOND_GEN;
```

TEST=Rebuilt coreboot; no warning was emitted.

Change-Id: Ibd83be8302e8a717db7e7dc86a403b5648976586
Signed-off-by: George Burgess IV <gbiv@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83412
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

0 files changed, 0 insertions, 0 deletions