Revert "libcamera: Adjust postview for rear camera."

This reverts commit d648f0c9e44519fb428d29c89998af991824be27.
Revert "libcamera: bump postview sizes"

This reverts commit 7b989c3a49b36c1b5aea9e24053c69b4412754ce.

Let's use a cleaner implementation of this fix (P1's method)
libcamera: Bump front camera postview sizes

* @pawitp noticed that libcamera uses PostviewHeap to store
  temporary YUV data, which is not large enough for
  1.3 MP selfies.
* However, bumping the values broke rear camera, which
  @bbelos noticed.
* Fix that by bumping the values only for the front camera.

Also-By: Pawit Pornkitprasan <p.pawit@gmail.com>
Also-By: Brian Beloshapka <bbelos@hotmail.com>
Change-Id: I139655bd12d752326a8237a86305b31c23fd0cad