riscv: Factor out page table TLB synchronization

The logic is the same for all page table levels. See commit 69be3fb1
("riscv: enable MMU_GATHER_RCU_TABLE_FREE for SMP && MMU").

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240327045035.368512-3-samuel.holland@sifive.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>