Input: goodix - use string-based chip ID

For Goodix GT917S chip, the chip ID string is "917S", which contains not
only numbers now.

Use string-based chip ID in the driver to support this chip and further
chips with alphanumber ID.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Reviewed-by: Bastien Nocera <hadess@hadess.net>
Link: https://lore.kernel.org/r/20200228010146.12215-3-icenowy@aosc.io


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>