iio: light: rpr0521: add missing Kconfig dependencies

Fix an implicit declaration of function error for rpr0521 under some configs

When CONFIG_RPR0521 is enabled without CONFIG_IIO_TRIGGERED_BUFFER,
the build results in "implicit declaration of function" errors, e.g.,
drivers/iio/light/rpr0521.c:434:3: error: implicit declaration of function
'iio_trigger_poll_chained' [-Werror=implicit-function-declaration]
434 | iio_trigger_poll_chained(data->drdy_trigger0);
| ^~~~~~~~~~~~~~~~~~~~~~~~

This fix adds select dependencies to RPR0521's configuration declaration.

Fixes: e12ffd241c00 ("iio: light: rpr0521 triggered buffer")
Signed-off-by: Paul Gazzillo <[e-mail]>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216678
Reviewed-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/20221110214729.ls5ixav5kxpeftk7@device
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/light/Kconfig

···
 	tristate "ROHM RPR0521 ALS and proximity sensor driver"
 	depends on I2C
 	select REGMAP_I2C
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
 	help
 	  Say Y here if you want to build support for ROHM's RPR0521
 	  ambient light and proximity sensor device.