clang-tidy: fix vpx_img_wrap align
clang-tidy: fix vpx_img_wrap align

This function specifically only aligns the stride and not the base buffer
like vpx_img_alloc does.

BUG=webm:1444

Change-Id: I3092827eeec3c9e16306a3973534d3a362a337e8

ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx