cputlb: remove tb_lock from tlb_flush functions

The acquisition of tb_lock was added when the async tlb_flush
was introduced in e3b9ca81 ("cputlb: introduce tlb_flush_* async work.")

tb_lock was there to allow us to do memset() on the tb_jmp_cache's.
However, since f3ced3c5 ("tcg: consistently access cpu->tb_jmp_cache
atomically") all accesses to tb_jmp_cache are atomic, so tb_lock
is not needed here. Get rid of it.
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NEmilio G. Cota <cota@braap.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

accel/tcg/cputlb.c

@@ -125,8 +125,6 @@ static void tlb_flush_nocheck(CPUState *cpu)
     atomic_set(&env->tlb_flush_count, env->tlb_flush_count + 1);
     tlb_debug("(count: %zu)\n", tlb_flush_count());
 
-    tb_lock();
-
     memset(env->tlb_table, -1, sizeof(env->tlb_table));
     memset(env->tlb_v_table, -1, sizeof(env->tlb_v_table));
     cpu_tb_jmp_cache_clear(cpu);
@@ -135,8 +133,6 @@ static void tlb_flush_nocheck(CPUState *cpu)
     env->tlb_flush_addr = -1;
     env->tlb_flush_mask = 0;
 
-    tb_unlock();
-
     atomic_mb_set(&cpu->pending_tlb_flush, 0);
 }
 
@@ -180,8 +176,6 @@ static void tlb_flush_by_mmuidx_async_work(CPUState *cpu, run_on_cpu_data data)
 
     assert_cpu_is_self(cpu);
 
-    tb_lock();
-
     tlb_debug("start: mmu_idx:0x%04lx\n", mmu_idx_bitmask);
 
     for (mmu_idx = 0; mmu_idx < NB_MMU_MODES; mmu_idx++) {
@@ -197,8 +191,6 @@ static void tlb_flush_by_mmuidx_async_work(CPUState *cpu, run_on_cpu_data data)
     cpu_tb_jmp_cache_clear(cpu);
 
     tlb_debug("done\n");
-
-    tb_unlock();
 }
 
 void tlb_flush_by_mmuidx(CPUState *cpu, uint16_t idxmap)