staging: r8188eu: evt_allocated_buf is not used

evt_allocated_buf in struct evt_priv is not used. Remove it.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220216081657.622467-2-martin@kaiser.cx


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