drm/gma500: remove set but not used variable 'channel_eq'

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

drivers/gpu/drm/gma500/cdv_intel_dp.c: In function cdv_intel_dp_complete_link_train:
drivers/gpu/drm/gma500/cdv_intel_dp.c:1596:7: warning: variable channel_eq set but not used [-Wunused-but-set-variable]

It is never used, so remove it.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1573902268-117518-1-git-send-email-zhengbin13@huawei.com

drivers/gpu/drm/gma500/cdv_intel_dp.c

@@ -1594,7 +1594,6 @@ cdv_intel_dp_complete_link_train(struct gma_encoder *encoder)
 {
 	struct drm_device *dev = encoder->base.dev;
 	struct cdv_intel_dp *intel_dp = encoder->dev_priv;
-	bool channel_eq = false;
 	int tries, cr_tries;
 	u32 reg;
 	uint32_t DP = intel_dp->DP;
@@ -1602,7 +1601,6 @@ cdv_intel_dp_complete_link_train(struct gma_encoder *encoder)
 	/* channel equalization */
 	tries = 0;
 	cr_tries = 0;
-	channel_eq = false;
 
 	DRM_DEBUG_KMS("\n");
 		reg = DP | DP_LINK_TRAIN_PAT_2;
@@ -1648,7 +1646,6 @@ cdv_intel_dp_complete_link_train(struct gma_encoder *encoder)
 
 		if (cdv_intel_channel_eq_ok(encoder)) {
 			DRM_DEBUG_KMS("PT2 train is done\n");
-			channel_eq = true;
 			break;
 		}