net: ionic: Fix error handling in ionic_init_module()

net: ionic: Fix error handling in ionic_init_module()

A problem about ionic create debugfs failed is triggered with the
following log given:

 [  415.799514] debugfs: Directory 'ionic' with parent '/' already present!

The reason is that ionic_init_module() returns ionic_bus_register_driver()
directly without checking its return value, if ionic_bus_register_driver()
failed, it returns without destroy the newly created debugfs, resulting
the debugfs of ionic can never be created later.

 ionic_init_module()
   ionic_debugfs_create() # create debugfs directory
   ionic_bus_register_driver()
     pci_register_driver()
       driver_register()
         bus_add_driver()
           priv = kzalloc(...) # OOM happened
   # return without destroy debugfs directory

Fix by removing debugfs when ionic_bus_register_driver() returns error.

Fixes: 22c2f0b535b9 ("ionic: Add hardware init and device commands")
Signed-off-by: Yuan Can <yuancan@huawei.com>
Acked-by: Shannon Nelson <snelson@pensando.io>
Link: https://lore.kernel.org/r/20221113092929.19161-1-yuancan@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>