staging: r8188eu: remove rtw_hal_enable_interrupt function

staging: r8188eu: remove rtw_hal_enable_interrupt function

Remove rtw_hal_enable_interrupt from hal/hal_intf.c, and remove its
declaration from include/hal_intf.h as well. This is just a wrapper
function that calls the function pointer enable_interrupt in struct
hal_ops if it is set, which it never is. In addition, this wrapper
function is unused anyway.

Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20210906010106.898-4-phil@philpotter.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>