kexec: move machine_kexec_post_load() to public interface

The kernel test robot reports the following compiler warning:

  | arch/arm64/kernel/machine_kexec.c:62:5: warning: no previous prototype for
  | function 'machine_kexec_post_load' [-Wmissing-prototypes]
  |    int machine_kexec_post_load(struct kimage *kimage)

Fix it by moving the declaration of machine_kexec_post_load() from
kexec_internal.h to the public header instead.
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/linux-arm-kernel/202102030727.gqTokACH-lkp@intel.comSigned-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/r/20210219195142.13571-1-pasha.tatashin@soleen.com
Fixes: 4c3c3123 ("arm64: kexec: move relocation function setup")
Signed-off-by: Will Deacon <will@kernel.org>

include/linux/kexec.h

@@ -309,6 +309,8 @@ extern void machine_kexec_cleanup(struct kimage *image);
 extern int kernel_kexec(void);
 extern struct page *kimage_alloc_control_pages(struct kimage *image,
 						unsigned int order);
+int machine_kexec_post_load(struct kimage *image);
+
 extern void __crash_kexec(struct pt_regs *);
 extern void crash_kexec(struct pt_regs *);
 int kexec_should_crash(struct task_struct *);

kernel/kexec_internal.h

@@ -13,8 +13,6 @@ void kimage_terminate(struct kimage *image);
 int kimage_is_destination_range(struct kimage *image,
 				unsigned long start, unsigned long end);
 
-int machine_kexec_post_load(struct kimage *image);
-
 extern struct mutex kexec_mutex;
 
 #ifdef CONFIG_KEXEC_FILE