ixgb: ROUND_UP macro cleanup in drivers/net/ixgb

IXGB_ROUNDUP macro cleanup ,use ALIGN

Signed-off-by: Milind Arun Choudhary <milindchoudhary@gmail.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>