loader: fix powerpc* ofw loader

With the introduction of llvm14, the powerpc* loader used on ofw/pseries
for 32 and 64 bit architectures puts the .data.rel.ro section after
.data section. This caused a crash kernel didn't boot. Bisect pointed to
change https://reviews.llvm.org/D111717 but problem could be fixed by
adding a section description to make it appear in the expected order.

This patch is based on discussion at:

https://github.com/llvm/llvm-project/issues/56306

MFC after: 1 day
Sponsored by: Instituto de Pesquisas Eldorado (eldorado.org.br)