libselinux: use correct name and content for patch 0004

Commit 62884096 ("libselinux: add
patch to fix build with gcc < 4.7") introduced a patch, but its file
name was incorrect, so it was never applied. In addition, the patch
was generated against the Git repository of SELinux, which includes
all projects, and therefore it doesn't apply to the libselinux source
code extracted from the tarball: the "libselinux/" component path
needs to be removed from the patch.

This commit fixes both problems, which should finally and really fix:

  http://autobuild.buildroot.net/results/c3272566bb808e43bb77ec59cfe596f7e0fe9a64/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>