powerpc/kernel: Add __init attribute to eligible functions

Some functions defined in `arch/powerpc/kernel` (and one in `arch/powerpc/
kexec`) are deserving of an `__init` macro attribute. These functions are
only called by other initialization functions and therefore should inherit
the attribute.
Also, change function declarations in header files to include `__init`.

Signed-off-by: Nick Child <nick.child@ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211216220035.605465-2-nick.child@ibm.com
diff --git a/arch/powerpc/include/asm/eeh.h b/arch/powerpc/include/asm/eeh.h
index b1a5bba..bd513fd 100644
--- a/arch/powerpc/include/asm/eeh.h
+++ b/arch/powerpc/include/asm/eeh.h
@@ -460,7 +460,7 @@ static inline void eeh_readsl(const volatile void __iomem *addr, void * buf,
 }
 
 
-void eeh_cache_debugfs_init(void);
+void __init eeh_cache_debugfs_init(void);
 
 #endif /* CONFIG_PPC64 */
 #endif /* __KERNEL__ */