staging: axis-fifo: remove unused pointer to memory resource

Remove unused resource pointer from the device's internal structure.

Signed-off-by: Quentin Deslandes <quentin.deslandes@itdev.co.uk>
Link: https://lore.kernel.org/r/20191101214232.16960-4-quentin.deslandes@itdev.co.uk


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