riscv: Annotate pgtable_l{4,5}_enabled with __ro_after_init

pgtable_l{4,5}_enabled are read only after initialization, make explicit
annotation of __ro_after_init on them.

Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240320064712.442579-3-dawei.li@shingroup.cn
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Dawei Li

arch/riscv/mm/init.c

@@ -49,8 +49,8 @@ u64 satp_mode __ro_after_init = SATP_MODE_32;
 EXPORT_SYMBOL(satp_mode);
 
 #ifdef CONFIG_64BIT
-bool pgtable_l4_enabled = !IS_ENABLED(CONFIG_XIP_KERNEL);
-bool pgtable_l5_enabled = !IS_ENABLED(CONFIG_XIP_KERNEL);
+bool pgtable_l4_enabled __ro_after_init = !IS_ENABLED(CONFIG_XIP_KERNEL);
+bool pgtable_l5_enabled __ro_after_init = !IS_ENABLED(CONFIG_XIP_KERNEL);
 EXPORT_SYMBOL(pgtable_l4_enabled);
 EXPORT_SYMBOL(pgtable_l5_enabled);
 #endif