ixgbe: remove obsolete irq_sem, add driver state checking code

After testing we confirmed that the irq_sem can safely be
removed from ixgbe.

Add strict state checking code to various ethtool parts to
properly protect against races between various driver reset
paths.

Signed-off-by: Ayyappan Veeraiyan <ayyappan.veeraiyan@intel.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>