powerpc/prom_init: Move __prombss to it's own section and store it in .bss

This makes __prombss its own section, and for now store
it in .bss.

This will give us the ability later to store it elsewhere
and/or free it after boot (it's about 8KB).
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/prom_init.c

@@ -48,7 +48,7 @@
 #include <linux/linux_logo.h>
 
 /* All of prom_init bss lives here */
-#define __prombss __initdata
+#define __prombss __section(.bss.prominit)
 
 /*
  * Eventually bump that one up

arch/powerpc/kernel/vmlinux.lds.S

@@ -4,6 +4,9 @@
 #else
 #define PROVIDE32(x)	PROVIDE(x)
 #endif
+
+#define BSS_FIRST_SECTIONS *(.bss.prominit)
+
 #include <asm/page.h>
 #include <asm-generic/vmlinux.lds.h>
 #include <asm/cache.h>