regmap: Use select .. if to get IRQ_DOMAIN enabled

Ensure that we can't get randconfig breakage by doing the IRQ_DOMAIN
select automatically. Don't just do the select from REGMAP_IRQ to ensure
that the select actually gets noticed.

Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/Kconfig

@@ -6,6 +6,7 @@ config REGMAP
 	default y if (REGMAP_I2C || REGMAP_SPI)
 	select LZO_COMPRESS
 	select LZO_DECOMPRESS
+	select IRQ_DOMAIN if REGMAP_IRQ
 	bool
 
 config REGMAP_I2C