staging: gpib: Add missing interface entry point

Declaring the driver entry points as static caused a warning
that the serial_poll_status function of the agilent_82350b driver
was unused.

Add the entry point to the corresponding interface structure
initializations where it was missing.

Fixes: 09a4655 ("staging: gpib: Add HP/Agilent/Keysight 8235xx PCI GPIB driver")
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/20250122103859.25499-2-dpenkler@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/gpib/agilent_82350b/agilent_82350b.c

@@ -842,6 +842,7 @@ static gpib_interface_t agilent_82350b_unaccel_interface = {
 	.primary_address = agilent_82350b_primary_address,
 	.secondary_address = agilent_82350b_secondary_address,
 	.serial_poll_response = agilent_82350b_serial_poll_response,
+	.serial_poll_status = agilent_82350b_serial_poll_status,
 	.t1_delay = agilent_82350b_t1_delay,
 	.return_to_local = agilent_82350b_return_to_local,
 };
@@ -869,6 +870,7 @@ static gpib_interface_t agilent_82350b_interface = {
 	.primary_address = agilent_82350b_primary_address,
 	.secondary_address = agilent_82350b_secondary_address,
 	.serial_poll_response = agilent_82350b_serial_poll_response,
+	.serial_poll_status = agilent_82350b_serial_poll_status,
 	.t1_delay = agilent_82350b_t1_delay,
 	.return_to_local = agilent_82350b_return_to_local,
 };