egl: fix memory leak related to _eglRefreshDeviceList()

egl: fix memory leak related to _eglRefreshDeviceList()

Indeed, the unnecessary drmDevice objects were not freed.

For instance, this issue could be triggered with: "piglit/bin/egl_ext_platform_device -auto -fbo":
SUMMARY: AddressSanitizer: 2796 byte(s) leaked in 12 allocation(s).

Fixes: e39d72aec203 ("egl: only take render nodes into account when listing DRM devices")
Signed-off-by: Patrick Lerda <patrick9876@free.fr>
Reviewed-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22408>