allocator for jumbo frame.
o Removed unneeded jlist lock which was used to manage jumbo
buffers.
o Don't reinitialize hardware if MTU was not changed.
o Added additional check for minimal MTU size.
o Added a new tunable hw.skc.jumbo_disable to disable jumbo frame
support for the driver. The tunable could be set for systems that
do not need to use jumbo frames and it would save
(9K * number of Rx descriptors) bytes kernel memory.
o Jumbo buffer allocation failure is no longer critical error for
the operation of sk(4). If sk(4) encounter the allocation failure
it just disables jumbo frame support and continues to work without
user intervention.
With these changes jumbo frame performance of sk(4) was slightly
increased and users should not encounter jumbo buffer allocation
failure. Previously sk(4) tried to allocate physically contiguous
memory, 3388KB for 256 Rx descriptors. Sometimes that amount of
contiguous memory region could not be available for running systems
which in turn resulted in failure of loading the driver.
Tested by: Cy Schubert < Cy.Schubert () komquats dot com >
cdca0fe8be