Setting: Fix error when turn on wifi hotspot with long Chinese Ssid issue

The "error" is caused by beyond the limitation from driver layer
which wifi ssid characters can not exceed 32 bytes.

Add the codes to limit the characters of user input.

CRs-Fixed: 539994

Change-Id: I16adc3b08c86caf336b5272d27713134cb0d5211
(cherry picked from commit ade7deac)