y4minput.c: correct empty loop formatting
y4minput.c: correct empty loop formatting

prefer {}s over ';'

Change-Id: I563fc82717e1deb4f42a40e03dca318c6adaa0c1

mwgoldsmith/libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,Topopiccione/libvpx,mwgoldsmith/libvpx,Topopiccione/libvpx,webmproject/libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,mwgoldsmith/vpx,Topopiccione/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,webmproject/libvpx,webmproject/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx