net: cxgb3: Cleanup in_interrupt() usage

t3_sge_stop() is called from task context and from error handlers in
interrupt context. It relies on in_interrupt() to differentiate the
contexts.

in_interrupt() is deprecated as it is ill defined and does not provide what
it suggests.

Instead of replacing it with some other construct, simply split the
function into t3_sge_stop_dma(), which can be called from any context, and
t3_sge_stop() which can be only called from task context.

This has the advantage that any bogus invocation of t3_sge_stop() from
wrong contexts can be caught by debug kernels instead of being papered over
by the conditional.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>