powerpc/fadump: Fix section mismatch warning

With some compilers/configs fadump_setup_param_area() isn't inlined into
its caller (which is __init), leading to a section mismatch warning:

  WARNING: modpost: vmlinux: section mismatch in reference:
  fadump_setup_param_area+0x200 (section: .text.fadump_setup_param_area)
  -> memblock_phys_alloc_range (section: .init.text)

Fix it by adding an __init annotation.

Fixes: 683eab94 ("powerpc/fadump: setup additional parameters for dump capture kernel")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/all/20240515163708.3380c4d1@canb.auug.org.au/Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/all/202405140922.oucLOx4Y-lkp@intel.com/Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240516132631.347956-1-mpe@ellerman.id.au

arch/powerpc/kernel/fadump.c

@@ -1740,7 +1740,7 @@ static void __init fadump_process(void)
  * Reserve memory to store additional parameters to be passed
  * for fadump/capture kernel.
  */
-static void fadump_setup_param_area(void)
+static void __init fadump_setup_param_area(void)
 {
 	phys_addr_t range_start, range_end;