[IMP] web: improved image widget for mobile

  - Before it need a tap to show options
  - And Tap area was not enough for mobile

addons/web/static/src/less/form_view.less

@@ -251,6 +251,24 @@
                 cursor: pointer;
             }
         }
+        @media (max-width: @screen-xs-min) {
+            .o_form_image_controls{
+                position: initial;
+                opacity: 1;
+                > .fa{
+                    width: 50%;
+                    padding: 6px;
+                    margin: 0px;
+                    text-align: center;
+                    &.o_select_file_button{
+                        background: @odoo-brand-optional;
+                    }
+                    &.o_clear_file_button{
+                        background: @brand-danger;
+                    }
+                }
+            }
+        }
 
         &:hover .o_form_image_controls {
             opacity: 0.8;