s390x/css: fix bits must be zero check for TIC

According to the PoP bit positions 0-3 and 8-32 of the format-1 CCW must
contain zeros.  Bits 0-3 are already covered by cmd_code validity
checking, and bit 32 is covered by the CCW address checking.

Bits 8-31 correspond to CCW1.flags and CCW1.count.  Currently we only
check for the absence of certain flags.  Let's fix this.

Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Message-Id: <20170725224442.13383-3-pasic@linux.vnet.ibm.com>
Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
[CH: tweaked comment]
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
