Merging SPI slave with BLE_APP_UART

[hkarthik97]

I have merged two program SPI slave and ble_app_uart 

I am getting these two errors

undefined reference to `nrfx_spis_buffers_set'

undefined reference to `nrfx_spis_init'

[Jørgen Holmefjord]

Hi,

There are two ways this can happen:

1. You did not include the nrfx_spis.c source file to your project.
2. You did not enable the SPIS driver in your sdk_config.h file. If you are using the legacy driver API (nrf_drv_spis*), you need to set SPIS_ENABLED to 1, or set NRFX_SPIS_ENABLED to 1 if you are using the nrfx API directly (nrfx_spis*).

Best regards,
Jørgen