powerpc: Fix writable sections being moved into the rodata region

.data.rel.ro*  catches .data.rel.root_cpuacct, and the kernel crashes on
a store in css_clear_dir. At least we know read-only data protection is
working...

Fixes: b6adc6d ("powerpc/build: move .data.rel.ro, .sdata2 to read-only")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221116043954.3307852-1-npiggin@gmail.com

arch/powerpc/kernel/vmlinux.lds.S

@@ -142,7 +142,7 @@ SECTIONS
 #endif
 
 	.data.rel.ro : AT(ADDR(.data.rel.ro) - LOAD_OFFSET) {
-		*(.data.rel.ro*)
+		*(.data.rel.ro .data.rel.ro.*)
 	}
 
 	.branch_lt : AT(ADDR(.branch_lt) - LOAD_OFFSET) {