msm: dcvs: remove core name

Currently core_name is used to identify which core the dcvs operates on.
Instead use a type and the type num while registration with dcvs and
return an id (dcvs_core_id) upon successfull registration.

The dcvs_core_id is used by the clients of msm_dcvs to call upon its
apis viz. freq_start, freq_stop, msm_dcvs_idle etc.

The dcvs inturn uses the type num passed in at registration time to
invoke apis on the clients viz. set_freq, get_freq, idle_enable.

This further cleans up the internal dcvs add_core and get_core
implementation. One need not pass around the core_name and use the type
instead.

Change-Id: I1736f4befec02249eae969694c7b7696dc9cdb9d
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>