xen-netfront: Use setup_timer

Use the timer API function setup_timer instead of structure field
assignments to initialize a timer.

A simplified version of the Coccinelle semantic patch that performs
this transformation is as follows:

@change@
expression e, func, da;
@@

-init_timer (&e);
+setup_timer (&e, func, da);
-e.data = da;
-e.function = func;

Signed-off-by: Vaishali Thakkar <vthakkar1994@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>