In __iavf_set_coalesce, the driver checks both ec->rx_coalesce_usecs and
ec->tx_coalesce_usecs for validity. It does this via a chain if if/else-if
blocks. If every single branch of the series of if statements exited, this
would be fine. However, the rx_coalesce_usecs is checked against zero to
print an informative message if use_adaptive_rx_coalesce is enabled. If
this check is true, it short circuits the entire chain of statements,
preventing validation of the tx_coalesce_usecs field.

Indeed, since commit e792779e ("iavf: Prevent changing static ITR
values if adaptive moderation is on") the iavf driver actually rejects any
change to the tx_coalesce_usecs or rx_coalesce_usecs when
use_adaptive_tx_coalesce or use_adaptive_rx_coalesce is enabled, making
this checking a bit redundant.

Fix this error by removing the unnecessary and redundant checks for
use_adaptive_rx_coalesce and use_adaptive_tx_coalesce. Since zero is a
valid value, and since the tx_coalesce_usecs and rx_coalesce_usecs fields
are already unsigned, remove the minimum value check. This allows assigning
an ITR value ranging from 0-8160 as described by the printed message.

Fixes: 65e87c03 ("i40evf: support queue-specific settings for interrupt moderation")
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>