Invalid/ Missing register writes in ixgbe driver

[Ramla-I]

The following bugs are present in the ixgbe driver:

1. Write to reserved bit 31 of EIMC register in the clear_interrupts function
2. Write to reserved bits [15:12] of the DTXMXSZRQ register
3. Bits of RDRXCTL are not set by software. According to the datasheet:
   RDRXCTL.RSCFRSTSIZE is by default 0x8 and should be set to 0 by software.
   RDRXCTL.RSCACKC is by default 0 and should be set to 1 by software.
   RDRXCTL.FCOE_WRFIX is by default 0 and should be set to 1 by software.
4. The FCTRL register should only be modified/ updated when the RXCTRL.RXEN bit is set to 0, but the set_promisc function updates the filters after RXCTRL.RXEN is set.

[ackxolotl]

Thanks for reporting!