ezusb_read_pda() is invoked via ->read_pda() while firmware is loaded in
preemtible context.

Use ezusb_req_ctx_wait_compl() in ezusb_read_pda().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201113212252.2243570-7-bigeasy@linutronix.de