staging: comedi: Kconfig: fix config COMEDI_ADDI_APCI_3120 dependants

staging: comedi: Kconfig: fix config COMEDI_ADDI_APCI_3120 dependants

A merge conflict between commits
4d69899aca61a8f5731cd8fdfae624cd5df70b7d ("staging: comedi:
addi_apci_3120: use dma_alloc_coherent()") and
a76a769e3b56de4f60ba2797a31342a61aa7d8b5 ("staging: comedi: remove
comedi_fc module") left the COMEDI_ADDI_APCI_3120 config option
depending on VIRT_TO_BUS when it no longer needs to do so.  The
dependency was removed by the first commit and accidentally reinstated
by the second commit.  Remove the dependency again.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>