On reset and close, the ICR register is read to clear any pending
interrupts, but the value is simply ignored.  Avoid assigning the
value to a variable, to inhibit a warning from gcc 4.6.

Also fix a potential race condition in reset routines which clear
interrupts before disabling them.

Reported-by: Ralph Giles <giles@thaumas.net>
Tested-by: Ralph Giles <giles@thaumas.net>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

This commit replaces the current gPXE e1000 driver with one ported
from Intel source code available at

    http://sourceforge.net/projects/e1000/

which is upstream source for the Linux kernel e1000 drivers, and
should support most if not all PCI e1000 variants.

Signed-off-by: Marty Connor <mdc@etherboot.org>