linux-perf: Remove remaining source filenames from executable

linux-perf: Remove remaining source filenames from executable

When we build perf with -ffile-prefix-map, there are still 2
source directory names embedded in the executable:

1. The Documentation subdirectory, used as a fallback from the
   installed location.
2. The python subdirectory, used in the Python script test.

Remove (1) since it is an unnecessary fallback.  Change (2)
to the installed location.

Gbp-Pq: Topic debian
Gbp-Pq: Name linux-perf-remove-remaining-source-filenames-from-executable.patch