fsi: core: Check error number after calling ida_simple_get

If allocation fails, the ida_simple_get() will return error number.
So master->idx could be error number and be used in dev_set_name().
Therefore, it should be better to check it and return error if fails,
like the ida_simple_get() in __fsi_get_new_minor().

Fixes: 09aecfab ("drivers/fsi: Add fsi master definition")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20220111073411.614138-1-jiasheng@iscas.ac.cnSigned-off-by: Joel Stanley <joel@jms.id.au>

drivers/fsi/fsi-core.c

@@ -1314,6 +1314,9 @@ int fsi_master_register(struct fsi_master *master)
 
 	mutex_init(&master->scan_lock);
 	master->idx = ida_simple_get(&master_ida, 0, INT_MAX, GFP_KERNEL);
+	if (master->idx < 0)
+		return master->idx;
+
 	dev_set_name(&master->dev, "fsi%d", master->idx);
 	master->dev.class = &fsi_master_class;