cifs: prevent use-after-free by freeing the cfile later

In the Linux kernel, the following vulnerability has been resolved:

cifs: prevent use-after-free by freeing the cfile later

In smb2_compound_op we have a possible use-after-free which can cause hard to debug problems later on.

This was revealed during stress testing with KASAN enabled kernel. Fixing it by moving the cfile free call to a few lines below, after the usage.