powerpc/build: put sys_call_table in .data.rel.ro if RELOCATABLE

Const function pointers by convention live in .data.rel.ro if they need
to be relocated. Now that .data.rel.ro is linked into the read-only
region, put them in the right section. This doesn't make much practical
difference, but it will make the C conversion of sys_call_table a
smaller change as far as linking goes.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220916040755.2398112-8-npiggin@gmail.com

arch/powerpc/kernel/systbl.S

@@ -12,7 +12,11 @@
 
 #include <asm/ppc_asm.h>
 
+#ifdef CONFIG_RELOCATABLE
+.section .data.rel.ro,"aw"
+#else
 .section .rodata,"a"
+#endif
 
 #ifdef CONFIG_PPC64
 	.p2align	3