libvpx

Silience -wextra warnings in vp9_reconintra.c

The warning messages complained that there are unused arguments
in a few prediction modes. This structure was designed on purpose,
such that a wrapper function can cover all prediction mode cases
and make them readily accessible as an pointer array.

This commit silences such warnings.

Change-Id: I7036b6bdb70747e5327d8f6fceb154f100abc4c0