cmake: Install FindWaffle.cmake under $LIBDIR/cmake/waffle

Instead of installing to $PREFIX/share/waffle/cmake/Modules, now we
install at $LIBDIR/cmake/waffle.

For example, on debian amd64, it would appear at:
/usr/lib/x86_64-linux-gnu/cmake/waffle/FindWaffle.cmake

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Cc: Dylan Baker <baker.dylan.c@gmail.com>
debian: Add FindWaffle.cmake to libwaffle-dev package

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
debian: Release 1.5.0-2

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>