cypress_m8: Packet format is separate from characteristic size

The Cypress app note states that when using an 8 byte packet buffer
size that the packet format is modified (to be more compact).  However
I have since discovered that newer DeLorme Earthmate LT-20 devices
(those that are low speed USB with 8 byte packet size) STILL use the
format that is really supposed to correspond to 32 byte packets.
Further confusing things is the subsequent discovery that there are
actually two different types of LT-20 - older LT-20's use 32 byte
packets which is probably why this issue wasn't originally
encountered.  The solution here is to flag the packet format
separately from the buffer size.  Then at initialization time,
identify the correct combination and set it up.  This is a critical
fix for anyone with a newer LT-20.  Older devices and non-Earthmate
devices should remain unaffected by this change.  (If other devices
behave in this, uh, unexpected manner, it's now just a simple 1 line
change to fix them as well (change the pkt_fmt member for that
device).  Default behavior with this patch is still to drive the
format as per the app-note; of course for Earthmate devices this is
overridden.
Signed-off-by: NMike Isely <isely@pobox.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>