Non-USING_GLES2 platforms: Move default log file location.

It's been moved to g_Config.memCardDirectory/PSP/SYSTEM/Logs/ppsspp.log. Has the same behaviour as before: if the Logs folder doesn't exist, it won't log the file.

The reasoning for this: It keeps PPSSPP's files all together, and is the last remaining file as far as I know that won't work in a read-only directory in its present state.