moxtet: remove unused moxtet_type declaration

For some reason, moxtet_type was defined in moxtet.h, but never actually
used.  Looks like a left-over from the original commit that was
exporting the moxtet bus type, but that wasn't needed, and it was a
different variable name, so no one noticed this one dangling around.

Cc: Marek Behún <kabel@kernel.org>
Link: https://lore.kernel.org/r/2023121937-pants-heroics-17c1@gregkh


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>