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)

stand/powerpc/ofw/ldscript.powerpc

@@ -57,6 +57,7 @@ SECTIONS
   .sbss2     : { *(.sbss2)   }
   /* Adjust the address for the data segment to the next page up. */
   . = ((. + 0x1000) & ~(0x1000 - 1));
+  .data.rel.ro : { *(.data.rel.ro*) }
   .data    :
   {
     *(.data)