riscv: Call secondary mmu notifier when flushing the tlb

This is required to allow the IOMMU driver to correctly flush its own
TLB.

Reviewed-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://lore.kernel.org/r/20250113142424.30487-1-alexghiti@rivosinc.com


Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>