riscv: Mark KASAN tmp* page tables variables as static

tmp_pg_dir, tmp_p4d and tmp_pud are only used in kasan_init.c so they
should be declared as static.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202306282202.bODptiGE-lkp@intel.com/
Fixes: 96f9d4d ("riscv: Rework kasan population functions")
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20230704074357.233982-1-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

@@ -23,9 +23,9 @@
  */
 
 extern pgd_t early_pg_dir[PTRS_PER_PGD];
-pgd_t tmp_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
-p4d_t tmp_p4d[PTRS_PER_P4D] __page_aligned_bss;
-pud_t tmp_pud[PTRS_PER_PUD] __page_aligned_bss;
+static pgd_t tmp_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
+static p4d_t tmp_p4d[PTRS_PER_P4D] __page_aligned_bss;
+static pud_t tmp_pud[PTRS_PER_PUD] __page_aligned_bss;
 
 static void __init kasan_populate_pte(pmd_t *pmd, unsigned long vaddr, unsigned long end)
 {