Fix compilation warnings in libvpx (-Wunused-function)

Fix compilation warnings in libvpx (-Wunused-function)

Currently, there are 27 warnings saying:
> ../../third_party/libvpx_new/source/libvpx/vp9/encoder/vp9_denoiser.h:63:12:\
> warning: 'total_adj_strong_thresh' defined but not used [-Wunused-function]

It's because |total_adj_strong_thresh| is defined as static function in .h file.
So warning will appear in any file that includes the header but does not use
the function.

The suggested solution is to declare the static function as inline.

Bug: http://web.sec.samsung.net/bugzilla/show_bug.cgi?id=15496

Reviewed by: sns.park

Change-Id: Ic2173c0c3560256df1319d4344988618c71ec9a2
Signed-off-by: SeungSeop Park <sns.park@samsung.com>