powerpc/rtas: Make enter_rtas() private

There are no longer any users of enter_rtas() outside of rtas.c, so make
it "private", by moving the declaration inside rtas.c. Hopefully this
will encourage people to use one of the wrappers which takes the sharp
edges off the RTAS calling sequence.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/rtas.h

@@ -334,7 +334,6 @@ extern void (*rtas_flash_term_hook)(int);
 
 extern struct rtas_t rtas;
 
-extern void enter_rtas(unsigned long);
 extern int rtas_token(const char *service);
 extern int rtas_service_present(const char *service);
 extern int rtas_call(int token, int, int, int *, ...);

arch/powerpc/kernel/rtas.c

@@ -44,6 +44,9 @@
 #include <asm/mmu.h>
 #include <asm/topology.h>
 
+/* This is here deliberately so it's only used in this file */
+void enter_rtas(unsigned long);
+
 struct rtas_t rtas = {
 	.lock = __ARCH_SPIN_LOCK_UNLOCKED
 };