The xHCI 1.0 specification adds a new field to the fourth dword in an
isochronous TRB: the transfer burst count (TBC).  This field is only
non-zero for SuperSpeed devices.  Each SS endpoint sets the bMaxBurst
field in the SuperSpeed endpoint companion descriptor, which indicates how
many max-packet-sized "bursts" it can handle in one service interval.  The
device driver may choose to burst less max packet sized chunks each
service interval (which is defined by one TD).  The xHCI driver indicates
to the host controller how many bursts it needs to schedule through the
transfer burst count field.

This patch will only effect xHCI hosts that advertise 1.0 support (0x100)
in the HCI version field of their capabilities register.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>