Revert "Handle index register of a memory operation being the pseudo-register RIZ/EIZ"

This reverts commit 01262f75.

irdb-libs/libIRDB-core/src/operand_csx86.cpp

@@ -176,9 +176,6 @@ static uint32_t to_reg_number(const x86_reg &reg)
 		case X86_REG_R15D:
 		case X86_REG_R15W:
 			return 15;
-        case X86_REG_RIZ:
-        case X86_REG_EIZ:
-            return -1; // STARS_x86_R_none, RIZ/EIZ is a pseudo-register having constant value of 0
 		default: break;
 	}
 	assert(0);