cairo: fix CVE patches assigned wrong CVE number

CVE-2019-6461 and CVE-2019-6462 are fixed, but the reporting is
incorrect as the patch for CVE-2019-6461 is actually for CVE-2019-6462
and vice-versa.

This swaps both files and edit the CVE field to report the correct
identifier.

Cc: Quentin Schulz <foss+yocto@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>