bnx2x: added support for working with one msix irq.

Until now, the bnx2x driver needed at least 2 available msix interrupt
vectors in order to use msix. This patch add the possibility of configuring
msix when only one interrupt vector is available.
Notice this patch contains lines with over 80 characters, as it keeps print
strings in a single line.

Signed-off-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>