Bluetooth: PBAP: Ignore case during contact search

PBAP contact search is case sensitive , so the contact search
was failing when searched with small letter and vice versa,
leading to incomplete search result. Ignoring case while contact
searcg to fix this issue.

Change-Id: I6f7f1b3db67874d6b5a6dbcb95e662ed2837f03c
CRs-Fixed: 534640
(cherry picked from commit a2867f790a77fbfd4b9878b4918ef884aca20259)
(cherry picked from commit accd3e1c550d1ccb5d4eef07bfb427ca4553cdbe)
(cherry picked from commit a16cf342429037fb53a19712cdc0646297a961fe)