msm: ipc: Reorganize server hash table

QMI server(<service_id:instance_id>) info is maintained using a hash
table. The server's instance_id is used as the key to index into that
hash table to perform maintenance operations(add, lookup, delete).
The service_id values are well distributed than the instance_id values
and hence the operations on the hash table are not optimized. Optimize
the hash table operations by using server's service_id as the key to
index into the hash table.

While accessing the server hash table, the mutexes are locked and
unlocked inside the access functions. This introduces some race
conditions once the access functions return. So lock and unlock the
server hash table mutex outside the access functions.

CRs-Fixed: 415158
Change-Id: Id1ce6bbfc677df26ff209fd62dca8553c7d2b4a5
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>