igb: Fix PPS input and output using 3rd and 4th SDP

commit 207ce626 upstream.

Fix handling of the tsync interrupt to compare the pin number with
IGB_N_SDP instead of IGB_N_EXTTS/IGB_N_PEROUT and fix the indexing to
the perout array.

Fixes: cf99c1dd

 ("igb: move PEROUT and EXTTS isr logic to separate functions")
Reported-by: Matt Corallo <ntp-lists@mattcorallo.com>
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20230213185822.3960072-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>