firmware: dmi_scan: Fix UUID endianness for SMBIOS >= 2.6

firmware: dmi_scan: Fix UUID endianness for SMBIOS >= 2.6

The dmi_ver wasn't updated correctly before the dmi_decode method run
to save the uuid.

That resulted in "dmidecode -s system-uuid" and
/sys/class/dmi/id/product_uuid disagreeing. The latter was buggy and
this fixes it.

Reported-by: Federico Simoncelli <fsimonce@redhat.com>
Fixes: 3537c5d732f4 ("drivers/firmware/dmi_scan.c: fetch dmi version from SMBIOS if it exists")
Fixes: 7882b0fd708c ("dmi_scan: refactor dmi_scan_machine(), {smbios,dmi}_present()")
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Jean Delvare <jdelvare@suse.de>