Input: goodix - add minimum firmware size check

Input: goodix - add minimum firmware size check

Our goodix_check_cfg_* helpers do things like:

	int i, raw_cfg_len = cfg->size - 2;
	...
	if (check_sum != cfg->data[raw_cfg_len]) {

When cfg->size < 2, this will end up indexing the cfg->data array with
a negative value, which will not end well.

To fix this this commit adds a new GOODIX_CONFIG_MIN_LENGTH define and
adds a minimum size check for firmware-config files using this new define.

For consistency this commit also adds a new GOODIX_CONFIG_GT9X_LENGTH for
the length used for recent gt9xx and gt1xxx chips, instead of using
GOODIX_CONFIG_MAX_LENGTH for this, so that if other length defines get
added in the future it will be clear that the MIN and MAX defines should
contain the min and max values of all the other defines.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Bastien Nocera <hadess@hadess.net>
Link: https://lore.kernel.org/r/20200307121505.3707-9-hdegoede@redhat.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>