ppc: flush QEMU JIT after 68k cache changes

ppc: flush QEMU JIT after 68k cache changes

OS3.x/WarpOS can patch PPC code and page tables from the m68k side in shared RAM. QEMU does not see those writes through the PPC softmmu, so stale translation blocks can survive until the m68k/PPC handoff deadlocks.

Import the optional ppc_cpu_flush_jit hook, mark QEMU PPC code cache state dirty on 68040 instruction-cache and MMU ATC flushes, and consume one coalesced flush at the next m68k-to-PPC handoff. Skip the flush while the m68k is halted so PPC-only OS4 execution is not forced to retranslate continuously.