update the location of assert for REG_ZR check (#112294)

* update the location of assert for REG_ZR check

* encodeZRtoSP() in caller

Author: kunalspathak

src/coreclr/jit/emitarm64.cpp

@@ -8012,7 +8012,7 @@ void emitter::emitIns_R_S(instruction ins, emitAttr attr, regNumber reg1, int va
                 regNumber rsvdReg = codeGen->rsGetRsvdReg();
 
                 // add rsvd, fp, #imm
-                emitIns_R_R_Imm(INS_add, EA_8BYTE, rsvdReg, reg2, imm);
+                emitIns_R_R_Imm(INS_add, EA_8BYTE, rsvdReg, encodingZRtoSP(reg2), imm);
                 // str p0, [rsvd, #0, mul vl]
                 emitIns_R_R_I(ins, attr, reg1, rsvdReg, 0);
 
@@ -8285,7 +8285,7 @@ void emitter::emitIns_S_R(instruction ins, emitAttr attr, regNumber reg1, int va
                 regNumber rsvdReg = codeGen->rsGetRsvdReg();
 
                 // add rsvd, fp, #imm
-                emitIns_R_R_Imm(INS_add, EA_8BYTE, rsvdReg, reg2, imm);
+                emitIns_R_R_Imm(INS_add, EA_8BYTE, rsvdReg, encodingZRtoSP(reg2), imm);
                 // str p0, [rsvd, #0, mul vl]
                 emitIns_R_R_I(ins, attr, reg1, rsvdReg, 0);