qcacmn: Implement a light weight get_timestamp routine

For some 3rd party platforms, get_timestamp through legacy
kernel API is time costing. For spin_lock/unlock statistics
info, the resolution in ms level is enough. So use another
light weight API to save CPU resource for 3rd party
platforms only.

Change-Id: I9182f00adda0d3081a2c40b222ab37bb1ca9d6a1
CRs-Fixed: 2796263