libdrm: Update to 2.4.102

This update libdrm to the latest version which have all (-2) FreeBSD patches
upstream. I'd like to keep it that way so please refrain from adding patches
here.
2.4.101 release notes:
https://lists.freedesktop.org/archives/dri-devel/2020-April/261067.html
2.4.102 release notes:
https://lists.freedesktop.org/archives/dri-devel/2020-May/267255.html

No timeline in https://abi-laboratory.pro/index.php?view=timeline&l=libdrm
but should be ok based on what I saw

Reviewed by: x11 (zeising)
Differential Revision: https://reviews.freebsd.org/D25023