riscv: Move create_tmp_mapping() to init sections

This function is only used at boot time so mark it as __init.

Fixes: 96f9d4d ("riscv: Rework kasan population functions")
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20230704074357.233982-2-alexghiti@rivosinc.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Alexandre Ghiti

arch/riscv/mm/kasan_init.c

@@ -439,7 +439,7 @@ static void __init kasan_shallow_populate(void *start, void *end)
 	kasan_shallow_populate_pgd(vaddr, vend);
 }
 
-static void create_tmp_mapping(void)
+static void __init create_tmp_mapping(void)
 {
 	void *ptr;
 	p4d_t *base_p4d;