Fix Lenovo T460 failure to suspend (sleep) under Linux

My Lenovo T460 with Intel integrated graphics abruptly stopped suspending properly a few weeks ago and it's been driving me nuts. Today I fixed it.

TL;DR: For my specific issue lowering the integrated graphics memory portal from 512MB to 256MB in the UEFI firmware setup ("BIOS setup", F1 boot menu) resolved the issue.

Updating Lenovo T460 BIOS (UEFI, firmware) without a CD on Linux

Some of Lenovo's newer models come with a firmware update distribution compatible with fwupd so you can just do a firmware update directly from the shell.

This is not the case for the T460, which has a bootable ISO, or a Windows installer that ... creates a bootable ISO.

I couldn't find my USB CD/DVD drive so I landed up finding a workaround.