linux-yocto: Enable powerpc-debug fragment for ppc64 LE

qemuppc64 is LE by default, this fixes kernel build for qemuppc64 with
gcc12

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit f1674f1a)
Signed-off-by: Steve Sakoman <steve@sakoman.com>