public showPassword: boolean = false;
public showHide(): void
{
this.showPassword = !this.showPassword;
}
...
<div class="col-12 placeholder">
<ion-input [type]="showPassword ? 'text' : 'password'" class="col-12" placeholder="Senha" [(ngModel)]="pwd"></ion-input>
<ion-icon [name]="showPassword ? 'eye-off' : 'eye'" (click)="showHide()"></ion-icon>
</div>