topology: pre-processor: Add support for conditional includes

topology: pre-processor: Add support for conditional includes

Add a new keyword "IncludeByKey" that will be used to conditional
include configuration files based on the argument value supplied during
build time. For example:

IncludeByKey.DMIC_CH_COUNT {
	"[1-4]"	"include/platform/intel/dmic-generic.conf"
}

The above config will include the dmic-generic.conf file if the argument
value for DMIC_CH_COUNT is between 1 and 4.

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>