riscv: enable software resend of irqs

The PLIC specification does not describe the interrupt pendings bits as
read-write, only that they "can be read". To allow for retriggering of
interrupts (and the use of the irq debugfs interface) enable
HARDIRQS_SW_RESEND for RISC-V.

Link: https://github.com/riscv/riscv-plic-spec/blob/master/riscv-plic.adoc#interrupt-pending-bits


Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Tested-by: Palmer Dabbelt <palmer@rivosinc.com> # on QEMU
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/r/20220729111116.259146-1-conor.dooley@microchip.com


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