newfs_msdos: Set sectors per fat once

There was an issue causing the fat size to shrink too small, causing
a fsck check to fail.

Bug: 17949028
Bug: 17761281
Change-Id: Id0207f2ab44e57ff81f5a53494b45344822a6495
Signed-off-by: Daniel Rosenberg <drosen@google.com>
1 file changed