media: i2c: isl7998x: drop of_match_ptr for ID table

The driver will match mostly by DT table (even thought there is regular
ID table) so there is little benefit in of_match_ptr (this also allows
ACPI matching via PRP0001, even though it might not be relevant here).
This also fixes !CONFIG_OF error:

  drivers/media/i2c/isl7998x.c:1557:34: error: ‘isl7998x_of_match’ defined but not used [-Werror=unused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/i2c/isl7998x.c

@@ -1611,7 +1611,7 @@ static const struct dev_pm_ops isl7998x_pm_ops = {
 static struct i2c_driver isl7998x_i2c_driver = {
 	.driver = {
 		.name = "isl7998x",
-		.of_match_table = of_match_ptr(isl7998x_of_match),
+		.of_match_table = isl7998x_of_match,
 		.pm = &isl7998x_pm_ops,
 	},
 	.probe		= isl7998x_probe,