graphics/llpp: Fix 'crashes Firefox sometimes'

• This one is related to bug #199872 where Firefox would randomly crash when exiting llpp (sometimes yes and sometimes no, you don't know which beforehand). Firefox (or GTK+ apps in general) seems to monitor ~/.config (not sure if true). llpp writes to ~/.config/llpp.conf when it exits, which will trigger bug #199872.
• This patch moves llpp's config file to ~/.llpp.conf instead, solving this annoyance.

PR: 214458
Submitted by: Tobias Kortkamp <t@tobik.me> (maintainer)