topology: Store number of strings of a text section

topology: Store number of strings of a text section

Enum controls may use text elements and need the number of strings.

This patch adds a text child object for a generic element. When parsing
a text section from the configuation file, store the text strings and
number of strings (num_items) in the text child object of the element.

Reported-by: G Kranthi <gudishax.kranthikumar@intel.com>
Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>