From: Christoph Hellwig <hch@lst.de>

I've just grepped over the tree for reamining MOD_INC_USE_COUNT users, and
ftape is a really horrible one, it relies on MOD_{INC,DEV}_USE_COUNT in the
most horrible places + it's own bookkepping and the <= 2.4 may unload
hooks.  And although I don't have the hardware I can guarantee it doesn't
work as expected.

So let's just remove the module_exit handler and mark it unremovable, if
someone wants to fix up ftape later it's fine with me, but it's a really
scary driver..