Input: pm8941-powerkey - fix debounce on gen2+ PMICs

Since PM8998/PM660, the power key debounce register was redefined to
support shorter debounce times. On PM8941 the shortest debounce time
(represented by register value 0) was 15625us, on PM8998 the shortest
debounce time is 62us, with the default being 2ms.

Adjust the bit shift to correctly program debounce on PM8998 and newer.

Fixes: 68c581d5

 ("Input: add Qualcomm PM8941 power key driver")
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Link: https://lore.kernel.org/r/20230529-pm8941-pwrkey-debounce-v1-2-c043a6d5c814@linaro.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>