drm/omap: Remove set but not used variable 'err' in hdmi4_audio_config

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/gpu/drm/omapdrm/dss/hdmi4_core.c: In function hdmi4_audio_config:
drivers/gpu/drm/omapdrm/dss/hdmi4_core.c:689:6: warning: variable err set but not used [-Wunused-but-set-variable]

It is not used since commit f5bab222 ("OMAPDSS:
HDMI: Add OMAP5 HDMI support")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1570518949-47574-5-git-send-email-zhengbin13@huawei.com

drivers/gpu/drm/omapdrm/dss/hdmi4_core.c

@@ -676,7 +676,7 @@ int hdmi4_audio_config(struct hdmi_core_data *core, struct hdmi_wp_data *wp,
 	struct hdmi_audio_format audio_format;
 	struct hdmi_audio_dma audio_dma;
 	struct hdmi_core_audio_config acore;
-	int err, n, cts, channel_count;
+	int n, cts, channel_count;
 	unsigned int fs_nr;
 	bool word_length_16b = false;
 
@@ -738,7 +738,7 @@ int hdmi4_audio_config(struct hdmi_core_data *core, struct hdmi_wp_data *wp,
 		return -EINVAL;
 	}
 
-	err = hdmi_compute_acr(pclk, fs_nr, &n, &cts);
+	hdmi_compute_acr(pclk, fs_nr, &n, &cts);
 
 	/* Audio clock regeneration settings */
 	acore.n = n;