qemu.conf: Make nvram list obsolete

Now that libvirt has firmware auto selection feature the nvram
config knob is more or less obsolete. It still makes sense in
cases where distro users are using does not provide FW descriptor
files, therefore I'm not removing it.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>

src/qemu/qemu.conf

@@ -740,6 +740,14 @@
 
 # Location of master nvram file
 #
+# This configuration option is obsolete. Libvirt will follow the
+# QEMU firmware metadata specification to automatically locate
+# firmware images. See docs/interop/firmware.json in the QEMU
+# source tree. These metadata files are distributed alongside any
+# firmware images intended for use with QEMU.
+#
+# ------------------------------------------
+#
 # When a domain is configured to use UEFI instead of standard
 # BIOS it may use a separate storage for UEFI variables. If
 # that's the case libvirt creates the variable store per domain