hw/riscv/riscv-iommu: Remove redundant struct members

Initially, the IOMMU would create a thread, but this thread was removed in
the merged version. The struct members for thread control should have been
removed as well, but they were not removed in commit 0c54acb8243
("hw/riscv: add RISC-V IOMMU base emulation").

Signed-off-by: Jason Chien <jason.chien@sifive.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250115141730.30858-1-jason.chien@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/riscv/riscv-iommu.h

@@ -58,11 +58,6 @@ struct RISCVIOMMUState {
     /* interrupt notifier */
     void (*notify)(RISCVIOMMUState *iommu, unsigned vector);
 
-    /* IOMMU State Machine */
-    QemuThread core_proc; /* Background processing thread */
-    QemuCond core_cond;   /* Background processing wake up signal */
-    unsigned core_exec;   /* Processing thread execution actions */
-
     /* IOMMU target address space */
     AddressSpace *target_as;
     MemoryRegion *target_mr;