Reload microcode on update

```bash
# /etc/pacman.d/hooks/microcode_reload.hook
[Trigger]
Operation = Upgrade
Type = Path
Target = usr/lib/firmware/amd-ucode/*

[Action]
Description = Applying CPU microcode updates...
When = PostTransaction
Depends = sh
Exec = /bin/sh -c 'echo 1 > /sys/devices/system/cpu/microcode/reload'
```