touch: common: modify the return value when register_tbn failed

Return 0 when the tbn_context doesn't exist because tbn is not an
always on feature.

Bug: 186717670
Bug: 190339589
Test: flash boot and vendor_boot.

Signed-off-by: davidycchen <davidycchen@google.com>
Change-Id: I4a842b53b4efaa89116ecedbabd82bbf1a311e71