media_build using regmap-i2c

Hi!

I noticed for a media_build installation, that tda10071 was not loadable because regmap-i2c did not exist.

The only way I saw to get regmap-i2c compiled, is to enable any other kernel module that has a "select REGMAP_I2C" in Kconfig.
I choose "CONFIG_SENSORS_ADS7828=m".

Maybe the kernel needs a way to enable this module "for external drivers" as the "Library routines" folders.

Regards
Matthias