Loopfilter MultiThread Optimization

Loopfilter MultiThread Optimization

Adding LPF within the tileworker hook. This means that LPF will be done
immediately after decode, without waiting for all threads to sync.

Performance Improvement -

Platform        Resolution      2 Threads       4 Threads
X86             720p            7.24%           22.04%
                1080p           5.29%           17.02%
ARM             720p            4.61%           8.75%
                1080p           5.55%           12.03%

x86 Improvement measured on Intel Core i7-6700 CPU @ 2.10GHz set
in performance with turbo mode off
ARM Improvement measured on Nexus 6 Snapdragon 805 Quad-core  @ 2.65 GHz

Change-Id: Ifa73c71b40db3fa7fa16f54f4e3aa06d1258caae