scsi_cd: CD_FLAG_VALID_MEDIA is sufficient to set d_sectorsize and
d_mediasize

[Forced commit to correct PR number.]
CD_FLAG_VALID_TOC is not required for setting those media properties.

PR: kern/138789
Submitted by: Juergen Lock <nox@jelal.kn-bremen.de>

		a slightly different version

Tested by: Pavel Sukhoy <sukhoy@ripn.net>,

		Markus Wild <m.wild@cybernet.ch>,
		Juergen Lock <nox@jelal.kn-bremen.de>,
		uqs

MFC after: 1 week