[PATCH] iio: Fix build error for ltc2664

[Jinjie Ruan]

If REGMAP_SPI is n and LTC2664 is y, the following build error occurs:

	riscv64-unknown-linux-gnu-ld: drivers/iio/dac/ltc2664.o: in function `ltc2664_probe':
	ltc2664.c:(.text+0x714): undefined reference to `__devm_regmap_init_spi'

Select REGMAP_SPI for LTC2664 to fix it.

Fixes: 4cc2fc445d2e ("iio: dac: ltc2664: Add driver for LTC2664 and LTC2672")
Signed-off-by: Jinjie Ruan <ruanjinjie at huawei.com>
---
 drivers/iio/dac/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 45e337c6d256..ae6d04c758d1 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -381,6 +381,7 @@ config LTC2664
 	tristate "Analog Devices LTC2664 and LTC2672 DAC SPI driver"
 	depends on SPI
 	select REGMAP
+	select REGMAP_SPI
 	help
 	  Say yes here to build support for Analog Devices
 	  LTC2664 and LTC2672 converters (DAC).
-- 
2.34.1