PCI: endpoint: pci-epf-vntb: Add epf_ntb_mw_bar_clear() num_mws kernel-doc

PCI: endpoint: pci-epf-vntb: Add epf_ntb_mw_bar_clear() num_mws kernel-doc

8e4bfbe644a6 ("PCI: endpoint: pci-epf-vntb: fix error handle in
epf_ntb_mw_bar_init()") added a "num_mws" parameter to
epf_ntb_mw_bar_clear() but failed to add kernel-doc for num_mws.

Add kernel-doc for num_mws on epf_ntb_mw_bar_clear().

Fixes: 8e4bfbe644a6 ("PCI: endpoint: pci-epf-vntb: fix error handle in epf_ntb_mw_bar_init()")
Link: https://lore.kernel.org/r/20230103024907.293853-1-yangyingliang@huawei.com
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>