The rk3399 scans the spi_bus_type to find the rt5514 driver, but does not
actually have a Kconfig dependency on SPI, so we can end up with a link
failure:

sound/soc/codecs/snd-soc-rt5514-spi.o: In function `rt5514_spi_driver_init':
rt5514-spi.c:(.init.text+0x14): undefined reference to `__spi_register_driver'
sound/soc/codecs/snd-soc-rt5514-spi.o: In function `rt5514_spi_burst_read':
rt5514-spi.c:(.text.rt5514_spi_burst_read+0x18c): undefined reference to `spi_sync'
sound/soc/codecs/snd-soc-rt5514-spi.o: In function `rt5514_spi_burst_write':
rt5514-spi.c:(.text.rt5514_spi_burst_write+0x1b4): undefined reference to `spi_sync'
sound/soc/rockchip/snd-soc-rk3399-gru-sound.o: In function `rockchip_sound_probe':
rk3399_gru_sound.c:(.text.rockchip_sound_probe+0x128): undefined reference to `spi_bus_type'

This adds the missing dependency.

Fixes: c6eac8a3 (ASoC: rockchip: Add machine driver for RK3399 GRU Boards)
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Xing Zheng <zhengxing@rock-chips.com>
Signed-off-by: Mark Brown <broonie@kernel.org>