unmounted filesystems start as ejected

[dhalbert]

Fixes #3709.

Undoes bda3267 from #3680. The problem is that a board that starts unconnected does not start with unejected drives; they should be ejected when boot.py is entered.

The original change saved 20 bytes. I tried reversing the sense of the ejected[] array, calling it not_ejected[]. (mounted was too confusing, because it has two meanings: one for TinyUSB, and one for the filesystem.) But the code was harder to read and the change caused the addition of a little extra code elsewhere to reverse the sense of various tests. So it ended up that only 12 bytes were saved. I think that was not worth the cost of harder-to-read-code.

This fix is only needed for main: the original change was done after 6.0.0.

Tested via boot.py on a QTPy.

[tannewt]

Thank you!