staging: r8188eu: support interface is always usb

We set ODM_CMNINFO_INTERFACE to ODM_ITRF_USB as this driver supports
only usb. Therefore, dm_odm->SupportInterface is always ODM_ITRF_USB.

Simplify some if conditions accordingly. Remove/replace two empty
functions.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211005200821.19783-9-martin@kaiser.cx


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