PCI: endpoint: pci-epf-vntb: fix error handle in epf_ntb_mw_bar_init()

In error case of epf_ntb_mw_bar_init(), memory window BARs should be
cleared, so add 'num_mws' parameter in epf_ntb_mw_bar_clear() and
calling it in error path to clear the BARs. Also add missing error
code when pci_epc_mem_alloc_addr() fails.

Fixes: ff32fac00d97 ("NTB: EPF: support NTB transfer between PCI RC and EP connection")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>