staging: gpib: Enable SRQ irq on request_system_control

The SRQ irq was being enabled on attach but the board is not
set up to handle it until it becomes system controller.

Move the enabling of the SRQ irq to bb_request_system_control.

Fixes: 4cd654f ("staging: gpib: Add gpio bitbang GPIB driver")
Tested-by: Dave Penkler <dpenkler@gmail.com>
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Link: https://lore.kernel.org/r/20250418173434.2892-4-dpenkler@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: dpenkler

drivers/staging/gpib/gpio/gpib_bitbang.c

@@ -884,6 +884,8 @@ static int bb_go_to_standby(struct gpib_board *board)
 
 static int bb_request_system_control(struct gpib_board *board, int request_control)
 {
+	struct bb_priv *priv = board->private_data;
+
 	dbg_printk(2, "%d\n", request_control);
 	if (!request_control)
 		return -EINVAL;
@@ -895,6 +897,8 @@ static int bb_request_system_control(struct gpib_board *board, int request_contr
 
 	gpiod_direction_input(SRQ);
 
+	ENABLE_IRQ(priv->irq_SRQ, IRQ_TYPE_EDGE_FALLING);
+
 	return 0;
 }
 
@@ -1299,8 +1303,6 @@ static int bb_attach(struct gpib_board *board, const struct gpib_board_config *c
 		       IRQF_TRIGGER_NONE))
 		goto bb_attach_fail_r;
 
-	ENABLE_IRQ(priv->irq_SRQ, IRQ_TYPE_EDGE_FALLING);
-
 	dbg_printk(0, "attached board %d\n", board->minor);
 	goto bb_attach_out;