padding-left style binding toggle doesn't work on Ivy

# 🐞 bug report

### Affected Package

The issue is caused by package @angular/....

### Is this a regression?

Yes, the previous version in which this bug was not present was: ....
Angular 6
see working Stackblitz here
https://stackblitz.com/edit/angular-issue-repro2-qbdodz

1. click the toggle button, it sets "customPadding" which just means padding-left only.
2. click the toggle button, it unsets "customPadding" which just means padding only.
3. Notice that the box has left padding set correctly.

### Description

When I use a Hostbinding for style, the first time I apply padding, it works, then if I apply padding-left, it works, then when I apply padding again, it is actually being applied as padding-top, padding-right, and padding-bottom, but not padding-left.

## 🔬 Minimal Reproduction

https://stackblitz.com/edit/angular-ivy-kajdf3

1. click the toggle button, it sets "customPadding" which just means padding-left only.
2. click the toggle button, it unsets "customPadding" which just means padding only.
3. Notice that the box does not have left padding set correctly.

## 🌍 Your Environment

**Angular Version:**

Angular CLI: 9.1.1

Node: 10.16.0

OS: win32 x64

Angular:

...

Ivy Workspace:

Package                      Version

------------------------------------------------------

@angular-devkit/architect    0.901.1

@angular-devkit/core         9.1.1

@angular-devkit/schematics   9.1.1

@schematics/angular          9.1.1

@schematics/update           0.901.1

rxjs                         6.5.4

**Anything else relevant?**