bnxt_en: Fix kernel panic during driver unload after attach failure

[chandrakanth.patil_broadcom.com]

Summary

Fixed a kernel panic that occurred when unloading the driver after bnxt_attach_pre()
failed. The iflib layer requires that all resources allocated in bnxt_attach_pre() be
freed before returning on failure. Failure to do so caused memory leaks, leading to a
panic during driver unload.

The fix ensures proper cleanup of all resources allocated in bnxt_attach_pre() before
returning an error.