Previously, all non-compressed formats were satisfied with a 4-byte
alignment.  The introduction of float formats changes this.

This change calculates the necessary alignment using the same code path
as compressed formats.

Also fixes RGB9E5's pixelByte being calculated as 3 instead of 4.

Bug: angleproject:3731
Change-Id: I6abfd1c294e7f863eb99d2468eaac09e5d714039
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1715205Reviewed-by: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>