Rather than checking every chip revision, introduce more flags to

Rather than checking every chip revision, introduce more flags to
mark controller's capability. Controllers that have jumbo frame
support sets MSK_FLAG_JUMBO, and controllers that does not support
checksum offloading for jumbo frames will set MSK_FLAG_JUMBO_NOCSUM.
For Fast Ethernet controllers it will set MSK_FLAG_FASTETHER and it
would be used in link state handling.

While here, disable Tx checksum offloading if jumbo frame is used
on controllers that does not have Tx checksum offloading capability
for jumbo frame(e.g. Yukon EC Ultra).