e1000e: test for unusable MSI support

e1000e: test for unusable MSI support

Some systems do not like 82571/2 use of 16-bit MSI messages and some
other systems claim to support MSI, but neither really works.  Setup a
test MSI handler to detect whether or not MSI is working properly, and
if not, fallback to legacy INTx interrupts.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>