staging/fwserial: Convert timers to use timer_setup()

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly. Also removes redundant initialization
of fw transaction timer, which already gets initialized per-transaction.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Bhumika Goyal <bhumirks@gmail.com>
Cc: devel@driverdev.osuosl.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>