[intel] Correct definition of receive overrun bit

Reported-by: Robin Smidsrød <robin@smidsrod.no>
Tested-by: Robin Smidsrød <robin@smidsrod.no>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/intel.h

 #define INTEL_IRQ_TXQE		0x00000002UL	/**< Transmit queue empty */
 #define INTEL_IRQ_LSC		0x00000004UL	/**< Link status change */
 #define INTEL_IRQ_RXDMT0	0x00000010UL	/**< Receive queue low */
+#define INTEL_IRQ_RXO		0x00000040UL	/**< Receive overrun */
 #define INTEL_IRQ_RXT0		0x00000080UL	/**< Receive timer */
-#define INTEL_IRQ_RXO		0x00000400UL	/**< Receive overrun */
 
 /** Interrupt Mask Set/Read Register */
 #define INTEL_IMS 0x000d0UL