target/arm: Simplify BFXIL expansion

The mask implied by the extract is redundant with the one
implied by the deposit.  Also, fix spelling of BFXIL.
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190514011129.11330-3-richard.henderson@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/translate-a64.c

@@ -4043,8 +4043,8 @@ static void disas_bitfield(DisasContext *s, uint32_t insn)
             tcg_gen_extract_i64(tcg_rd, tcg_tmp, ri, len);
             return;
         }
-        /* opc == 1, BXFIL fall through to deposit */
-        tcg_gen_extract_i64(tcg_tmp, tcg_tmp, ri, len);
+        /* opc == 1, BFXIL fall through to deposit */
+        tcg_gen_shri_i64(tcg_tmp, tcg_tmp, ri);
         pos = 0;
     } else {
         /* Handle the ri > si case with a deposit
@@ -4062,7 +4062,7 @@ static void disas_bitfield(DisasContext *s, uint32_t insn)
         len = ri;
     }
 
-    if (opc == 1) { /* BFM, BXFIL */
+    if (opc == 1) { /* BFM, BFXIL */
         tcg_gen_deposit_i64(tcg_rd, tcg_rd, tcg_tmp, pos, len);
     } else {
         /* SBFM or UBFM: We start with zero, and we haven't modified