staging: rtl8712: fix error handling in r871xu_drv_init

staging: rtl8712: fix error handling in r871xu_drv_init

Previous error handling path was unique for all
possible errors and there was unnecessary branching.
Also, one step for freeing drv_sw was missing. All
these problems was fixed by restructuring error
handling path.

Also, moved out free_netdev() from r8712_free_drv_sw() for
correct error handling.

Fixes: 2865d42c78a9 ("staging: r8712u: Add the new driver to the mainline kernel")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/febb00f72354449bb4d305f373d6d2f47e539ab4.1623620630.git.paskripkin@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>