video: fbdev: pxa3xx_gcu: 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.
This also fixes the use of the "priv" variable in QERROR(), since it was
pointing to struct timer_list, not struct pxa3xx_gcu_priv.