i40e: add mask to apply valid bits for itr_idx

[ Upstream commit eac04428abe9f9cb203ffae4600791ea1d24eb18 ]

The ITR index (itr_idx) is only 2 bits wide. When constructing the
register value for QINT_RQCTL, all fields are ORed together. Without
masking, higher bits from itr_idx may overwrite adjacent fields in the
register.

Apply I40E_QINT_RQCTL_ITR_INDX_MASK to ensure only the intended bits are
set.

Fixes: 5c3c48ac ("i40e: implement virtual device interface")
Cc: stable@vger.kernel.org
Signed-off-by: Lukasz Czapnik <lukasz.czapnik@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
[ Added missing linux/bitfield.h header for FIELD_PREP macro ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>