i40e: fix MMIO write access to an invalid page in i40e_clear_hw

i40e: fix MMIO write access to an invalid page in i40e_clear_hw

When the device sends a specific input, an integer underflow can occur, leading
to MMIO write access to an invalid page.

Prevent the integer underflow by changing the type of related variables.

Signed-off-by: Kyungwook Boo <bookyungwook@gmail.com>
Link: https://lore.kernel.org/lkml/ffc91764-1142-4ba2-91b6-8c773f6f7095@gmail.com/T/
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Rinitha S <sx.rinitha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>