of: fdt: Rename reserve_elfcorehdr() to fdt_reserve_elfcorehdr()

On ia64/allmodconfig:

    drivers/of/fdt.c:609:20: error: conflicting types for 'reserve_elfcorehdr'; have 'void(void)'
      609 | static void __init reserve_elfcorehdr(void)
	  |                    ^~~~~~~~~~~~~~~~~~
    arch/ia64/include/asm/meminit.h:43:12: note: previous declaration of 'reserve_elfcorehdr' with type 'int(u64 *, u64 *)' {aka 'int(long long unsigned int *, long long unsigned int *)'}
       43 | extern int reserve_elfcorehdr(u64 *start, u64 *end);
	  |            ^~~~~~~~~~~~~~~~~~

Fix this by prefixing the FDT function name with "fdt_".

Fixes: f7e7ce9 ("of: fdt: Add generic support for handling elf core headers property")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/f6eabbbce0fba6da3da0264c1e1cf23c01173999.1629884393.git.geert+renesas@glider.be
Signed-off-by: Rob Herring <robh@kernel.org>

Author: geertu

drivers/of/fdt.c

@@ -599,14 +599,14 @@ static int __init __fdt_scan_reserved_mem(unsigned long node, const char *uname,
 }
 
 /*
- * reserve_elfcorehdr() - reserves memory for elf core header
+ * fdt_reserve_elfcorehdr() - reserves memory for elf core header
  *
  * This function reserves the memory occupied by an elf core header
  * described in the device tree. This region contains all the
  * information about primary kernel's core image and is used by a dump
  * capture kernel to access the system memory on primary kernel.
  */
-static void __init reserve_elfcorehdr(void)
+static void __init fdt_reserve_elfcorehdr(void)
 {
 	if (!IS_ENABLED(CONFIG_CRASH_DUMP) || !elfcorehdr_size)
 		return;
@@ -647,7 +647,7 @@ void __init early_init_fdt_scan_reserved_mem(void)
 
 	of_scan_flat_dt(__fdt_scan_reserved_mem, NULL);
 	fdt_init_reserved_mem();
-	reserve_elfcorehdr();
+	fdt_reserve_elfcorehdr();
 }
 
 /**