powerpc/52xx: Add missing functions prototypes

The function prototypes were declared within a `#ifdef CONFIG_PPC_LITE5200`
block which would prevent them from being visible when compiling
`mpc52xx_pm.c`. Move the prototypes outside of the `#ifdef` block to fix
the following warnings treated as errors with W=1:

  arch/powerpc/platforms/52xx/mpc52xx_pm.c:58:5: error: no previous prototype for ‘mpc52xx_pm_prepare’ [-Werror=missing-prototypes]
  arch/powerpc/platforms/52xx/mpc52xx_pm.c:113:5: error: no previous prototype for ‘mpc52xx_pm_enter’ [-Werror=missing-prototypes]
  arch/powerpc/platforms/52xx/mpc52xx_pm.c:181:6: error: no previous prototype for ‘mpc52xx_pm_finish’ [-Werror=missing-prototypes]

Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/mpc52xx.h

@@ -350,14 +350,14 @@ extern struct mpc52xx_suspend mpc52xx_suspend;
 extern int __init mpc52xx_pm_init(void);
 extern int mpc52xx_set_wakeup_gpio(u8 pin, u8 level);
 
-#ifdef CONFIG_PPC_LITE5200
-extern int __init lite5200_pm_init(void);
-
 /* lite5200 calls mpc5200 suspend functions, so here they are */
 extern int mpc52xx_pm_prepare(void);
 extern int mpc52xx_pm_enter(suspend_state_t);
 extern void mpc52xx_pm_finish(void);
 extern char saved_sram[0x4000]; /* reuse buffer from mpc52xx suspend */
+
+#ifdef CONFIG_PPC_LITE5200
+int __init lite5200_pm_init(void);
 #endif
 #endif /* CONFIG_PM */