Draft: pmaports/linux-nokia-n900: upgrade to linux 6.1-rc7

Marking as draft because modem has issues. This is a long-standing problem [1] that has been workarounded by the 0005-kernel-dma-workaround-n900-modem-oops since around linux 5.15. For some reason, it isn't helping anymore, but will investigate further.

All other hardware works correctly with this kernel (as in previously packaged versions).

[1] https://marc.info/?l=linux-omap&m=163799095101818&w=2