staging: r8188eu: remove UsbRxAggMode from struct hal_data_8188e

UsbRxAggMode in struct hal_data_8188e is set to USB_RX_AGG_DMA and
never changed. Remove UsbRxAggMode from the hal_data_8188e structure
and remove related dead code.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220201084259.7497-8-straube.linux@gmail.com


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