Cannot compile slave side of split keyboards

[Lenbok]

Describe the Bug

As of merging #32 we can no longer compile the slave side of split keyboards, e.g:

$ make iris_ble/slave
[...]
Compiling: tmk_core/protocol/nrf/nrf52/adc.c                                                        [OK]
Compiling: tmk_core/protocol/nrf/sdk15/usbd.c                                                      tmk_core/protocol/nrf/sdk15/usbd.c: In function 'usbd_process':
tmk_core/protocol/nrf/sdk15/usbd.c:754:33: error: expected expression before ')' token
  754 |           if (!get_usb_enabled()) {
      |                                 ^
tmk_core/protocol/nrf/sdk15/usbd.c:756:30: error: macro "select_usb" passed 1 arguments, but takes just 0
  756 |               select_usb(true);
      |                              ^
In file included from tmk_core/protocol/nrf/sdk15/usbd.c:49:
tmk_core/protocol/nrf/app_ble_func.h:52: note: macro "select_usb" defined here
   52 | #define select_usb()
      |
tmk_core/protocol/nrf/sdk15/usbd.c:756:15: error: 'select_usb' undeclared (first use in this function); did you mean 'select'?
  756 |               select_usb(true);
      |               ^~~~~~~~~~
      |               select
tmk_core/protocol/nrf/sdk15/usbd.c:756:15: note: each undeclared identifier is reported only once for each function it appears in
tmk_core/protocol/nrf/sdk15/usbd.c:759:37: error: expected expression before ')' token
  759 |               if (!get_ble_enabled()) {
      |                                     ^
tmk_core/protocol/nrf/sdk15/usbd.c:766:33: error: expected expression before ')' token
  766 |           if (!get_ble_enabled()) { // USB POWER removed and battery present
      |                                 ^
 [ERRORS]
 |
 |
 |
make[1]: *** [tmk_core/rules.mk:362: .build/obj_iris_ble_slave_default/protocol/nrf/sdk15/usbd.o] Error 1
Make finished with errors
make: *** [Makefile:544: iris_ble/slave] Error 1

@karakum

[Lenbok]

Thank you, 6896849 fixes it!