target/mips: Convert Rel6 LWLE/LWRE/SWLE/SWRE opcodes to decodetree

LWLE/LWRE/SWLE/SWRE (EVA) opcodes have been removed from
the Release 6. Add a single decodetree entry for the opcodes,
triggering Reserved Instruction if ever used.

Remove unreachable check_insn_opc_removed() calls.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20201208203704.243704-11-f4bug@amsat.org>

target/mips/mips32r6.decode

@@ -20,6 +20,11 @@ REMOVED             010011 ----- ----- ----- ----- ------   # COP1X (COP3)
 
 REMOVED             011100 ----- ----- ----- ----- ------   # SPECIAL2
 
+REMOVED             011111 ----- ----- ----------  011001   # LWLE
+REMOVED             011111 ----- ----- ----------  011010   # LWRE
+REMOVED             011111 ----- ----- ----------  100001   # SWLE
+REMOVED             011111 ----- ----- ----------  100010   # SWRE
+
 REMOVED             100010 ----- ----- ----------------     # LWL
 REMOVED             100110 ----- ----- ----------------     # LWR
 REMOVED             101010 ----- ----- ----------------     # SWL

target/mips/translate.c

@@ -28121,8 +28121,6 @@ static void decode_opc_special3(CPUMIPSState *env, DisasContext *ctx)
         switch (op1) {
         case OPC_LWLE:
         case OPC_LWRE:
-            check_insn_opc_removed(ctx, ISA_MIPS_R6);
-            /* fall through */
         case OPC_LBUE:
         case OPC_LHUE:
         case OPC_LBE:
@@ -28134,8 +28132,6 @@ static void decode_opc_special3(CPUMIPSState *env, DisasContext *ctx)
             return;
         case OPC_SWLE:
         case OPC_SWRE:
-            check_insn_opc_removed(ctx, ISA_MIPS_R6);
-            /* fall through */
         case OPC_SBE:
         case OPC_SHE:
         case OPC_SWE: