drm/panel: ili9322: Remove redundant volatle_reg() operation

The ili9322 driver has a volatile_reg() operation in it's regmap which
always returns false. This is redundant since it is the default in the
regmap core, remove the operation for a trivial code size and performance
improvement.
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231001-drm-sn65dsi83-maple-v1-1-5519799a55e5@kernel.org

drivers/gpu/drm/panel/panel-ilitek-ili9322.c

@@ -325,11 +325,6 @@ static struct regmap_bus ili9322_regmap_bus = {
 	.val_format_endian_default = REGMAP_ENDIAN_BIG,
 };
 
-static bool ili9322_volatile_reg(struct device *dev, unsigned int reg)
-{
-	return false;
-}
-
 static bool ili9322_writeable_reg(struct device *dev, unsigned int reg)
 {
 	/* Just register 0 is read-only */
@@ -343,7 +338,6 @@ static const struct regmap_config ili9322_regmap_config = {
 	.val_bits = 8,
 	.max_register = 0x44,
 	.cache_type = REGCACHE_RBTREE,
-	.volatile_reg = ili9322_volatile_reg,
 	.writeable_reg = ili9322_writeable_reg,
 };