powerpc: Introduce asm-prototypes.h

Sparse picked up a number of functions that are implemented in C and
then only referred to in asm code.

This introduces asm-prototypes.h, which provides a place for
prototypes of these functions.

This silences some sparse warnings.

Signed-off-by: Daniel Axtens <dja@axtens.net>
[mpe: Add include guards, clean up copyright & GPL text]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/machine_kexec_64.c

@@ -29,6 +29,7 @@
 #include <asm/prom.h>
 #include <asm/smp.h>
 #include <asm/hw_breakpoint.h>
+#include <asm/asm-prototypes.h>
 
 #ifdef CONFIG_PPC_BOOK3E
 int default_machine_kexec_prepare(struct kimage *image)

arch/powerpc/kernel/smp.c

@@ -53,6 +53,7 @@
 #include <asm/vdso.h>
 #include <asm/debug.h>
 #include <asm/kexec.h>
+#include <asm/asm-prototypes.h>
 
 #ifdef DEBUG
 #include <asm/udbg.h>

arch/powerpc/kernel/traps.c

@@ -60,6 +60,7 @@
 #include <asm/switch_to.h>
 #include <asm/tm.h>
 #include <asm/debug.h>
+#include <asm/asm-prototypes.h>
 #include <sysdev/fsl_pci.h>
 
 #if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)