When using a kernel from Alpine the kernel configuration cannot be
found in pmaports. We cannot check the kernel config for missing
options in that case, but that's no reason to break the flasher
entirely.
Replace "args.logfd" with "pmb.helpers.logging.logfd" in order to avoid
passing "args" to all functions that only use it to write to logfd. This
is the first step to get rid of this args-passed-to-all-functions
pattern in pmbootstrap.
