radio: iris: Fix 64th character in  RDS RT field is missing

FM driver sends only upto 63 characters as Radio Text data
to upper layer.

Pass upto 64 characters as Radio Text

Change-Id: I3d49d85eb0c6e91ef0ea5660e572734a38281d62
CRs-Fixed: 505062
Signed-off-by: Ayaz Ahmad <aahmad@codeaurora.org>