ixgbevf: remove unused fields from struct ixgbevf_adapter

ixgbevf: remove unused fields from struct ixgbevf_adapter

Remove hw_rx_no_dma_resources and eitr_param fields from struct
ixgbevf_adapter since these fields are never referenced in the driver.

Note that the interrupt throttle rate is controlled by the
rx_itr_setting and tx_itr_setting variables.

This change simplifies the ixgbevf driver by removing unused fields,
which improves maintainability.

Signed-off-by: Yuto Ohnuki <ytohnuki@amazon.com>
Reviewed-by: Dawid Osuchowski <dawid.osuchowski@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>