[PATCH] don't mangle INQUIRY if cmddt or evpd bits are set

sbp2.c mangles INQUIRY response in a way that only applies to standard
inquiry data (i.e. when both cmddt and evpd bits are 0).  Leave other cases
alone; e.g. when asking for VPD the length of reply is in byte 3, not 4
and byte 4 is the first byte of device serial number.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>