tcg: Rename TCGMemOpIdx to MemOpIdx

We're about to move this out of tcg.h, so rename it
as we did when moving MemOp.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/tcg/tcg.c b/tcg/tcg.c
index 4142d42..658be0c 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -1910,7 +1910,7 @@
             case INDEX_op_qemu_ld_i64:
             case INDEX_op_qemu_st_i64:
                 {
-                    TCGMemOpIdx oi = op->args[k++];
+                    MemOpIdx oi = op->args[k++];
                     MemOp op = get_memop(oi);
                     unsigned ix = get_mmuidx(oi);