s390: remove unnecessary dcheck

R=joransiu@ca.ibm.com

Change-Id: I9209d2cc1da2b7397fc11fd884d2b44851e734b0
Reviewed-on: https://chromium-review.googlesource.com/1115376Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#54044}

src/compiler/s390/code-generator-s390.cc

@@ -3044,7 +3044,6 @@ void CodeGenerator::AssembleReturn(InstructionOperand* pop) {
     }
   }
   if (pop->IsImmediate()) {
-    DCHECK_EQ(Constant::kInt32, g.ToConstant(pop).type());
     pop_count += g.ToConstant(pop).ToInt32();
   } else {
     __ Drop(g.ToRegister(pop));

src/s390/assembler-s390.h

@@ -763,7 +763,6 @@ inline void rsy_format(Opcode op, int f1, int f2, int f3, int f4) {
     rsy_format(op_name, r1.code(), r3.code(), b2.code(), d2.immediate());  \
   }                                                                        \
   void name(Register r1, Register r3, Operand d2) {                        \
-    DCHECK_NE(d2.immediate(), 0);                                          \
     name(r1, r3, r0, d2);                                                  \
   }                                                                        \
   void name(Register r1, Register r3, const MemOperand& opnd) {            \