Settings: Fix error when input WLAN Direct name with long Chinese name

Caused by beyond the limitation from driver layer which the
characters of WLAN Direct name can not exceed 32 bytes.

Add the codes to limit the characters of user input.

CRs-Fixed: 646426

Change-Id: I1ddf6d69940e0685c159e1b6329e0ee5fbbac222
(cherry picked from commit d847a71f)