xen/pciback: Fix incorrect type warnings

xen/pciback: Fix incorrect type warnings

Correct enum pci_channel_io_normal should be used instead of putting
integer value 1.

Fix following smatch warnings:
drivers/xen/xen-pciback/pci_stub.c:805:40: warning: incorrect type in argument 2 (different base types)
drivers/xen/xen-pciback/pci_stub.c:805:40:    expected restricted pci_channel_state_t [usertype] state
drivers/xen/xen-pciback/pci_stub.c:805:40:    got int
drivers/xen/xen-pciback/pci_stub.c:862:40: warning: incorrect type in argument 2 (different base types)
drivers/xen/xen-pciback/pci_stub.c:862:40:    expected restricted pci_channel_state_t [usertype] state
drivers/xen/xen-pciback/pci_stub.c:862:40:    got int
drivers/xen/xen-pciback/pci_stub.c:973:31: warning: incorrect type in argument 2 (different base types)
drivers/xen/xen-pciback/pci_stub.c:973:31:    expected restricted pci_channel_state_t [usertype] state
drivers/xen/xen-pciback/pci_stub.c:973:31:    got int

Signed-off-by: Muhammad Usama Anjum <musamaanjum@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20210326181442.GA1735905@LEGION
Signed-off-by: Juergen Gross <jgross@suse.com>