USB: serial: mos7840: 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 e1, e2, e3, e4, a, b;
@@

-init_timer(&e1);
+setup_timer(&e1, a, b);

... when != a = e2
    when != b = e3

-e1.function = a;
... when != b = e4
-e1.data = b;

Signed-off-by: Vaishali Thakkar <vthakkar1994@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>