Revert "kmod-setup: don't print warning on -ENOSYS"

This partially reverts commit 78d298bb.
The changed coding-style is kept, but the ENOENT->ENOSYS conversion is
reverted.

kmod was fixed upstream to no longer return ENOSYS. Also see:
    https://git.kernel.org/cgit/utils/kernel/kmod/kmod.git/commit/?id=114ec87c85c35a2bd3682f9f891e494127be6fb5

The kmod fix is marked for backport, so no reason to bump the kmod
version we depend on.