PCI: endpoint: pci-epf-vntb: Remove duplicate resource teardown

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

PCI: endpoint: pci-epf-vntb: Remove duplicate resource teardown

epf_ntb_epc_destroy() duplicates the teardown that the caller is

supposed to perform later. This leads to an oops when .allow_link fails

or when .drop_link is performed. The following is an example oops of the

former case:

Unable to handle kernel paging request at virtual address dead000000000108

[...]

[dead000000000108] address between user and kernel address ranges

Internal error: Oops: 0000000096000044 [#1] SMP

[...]

Call trace:

pci_epc_remove_epf+0x78/0xe0 (P)

pci_primary_epc_epf_link+0x88/0xa8

configfs_symlink+0x1f4/0x5a0

vfs_symlink+0x134/0x1d8

do_symlinkat+0x88/0x138

__arm64_sys_symlinkat+0x74/0xe0

[...]

Remove the helper, and drop pci_epc_put(). EPC device refcounting is

tied to the configfs EPC group lifetime, and pci_epc_put() in the

.drop_link path is sufficient.