touch controller irq storm drains battery when screen is blanked

long known but i've not found a bug:

[ 4491.190334] edt_ft5x06 2-0038: Unable to fetch data, error: -6
[ 4496.132554] edt_ft5x06_ts_isr: 15686 callbacks suppressed

only happens when screen is blanked due to the way lcd and touch are wired up. i'll fix that.