i40e: remove fake support of rx-frames-irq

Since we never support this feature for I40E driver, we don't have to
display the value when using 'ethtool -c eth0'.

Before this patch applied, the rx-frames-irq is 256 which is consistent
with tx-frames-irq. Apparently it could mislead users.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20231213184406.1306602-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>