tpm/ppi: Constify static struct attribute_group

The only usage of ppi_attr_grp is to put its address in an array of
pointers to const struct attribute_group. Make it const to allow the
compiler to put it in read-only memory.
Signed-off-by: NRikard Falkeborn <rikard.falkeborn@gmail.com>
Reviewed-by: NJarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: NJarkko Sakkinen <jarkko@kernel.org>

drivers/char/tpm/tpm-chip.c

@@ -278,6 +278,8 @@ static void tpm_devs_release(struct device *dev)
 {
 	struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
 
+	dump_stack();
+
 	/* release the master device reference */
 	put_device(&chip->dev);
 }

drivers/char/tpm/tpm_ppi.c

@@ -358,7 +358,7 @@ static struct attribute *ppi_attrs[] = {
 	&dev_attr_tcg_operations.attr,
 	&dev_attr_vs_operations.attr, NULL,
 };
-static struct attribute_group ppi_attr_grp = {
+static const struct attribute_group ppi_attr_grp = {
 	.name = "ppi",
 	.attrs = ppi_attrs
 };