egl/drm: remove temporary fd variable

egl/drm: remove temporary fd variable

In all codepaths, this var ends up assigned to the struct, except one:
a cleanup codepath, where the `close()` was removed, leading to fd leaks.
Remove the temp fd and assign to the struct field directly instead.

CovID: 1213930
Fixes: 7ec07beedf486d8ab901 ("egl/drm: make use of the
                              dri2_display_destroy() helper")
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>