drm/amd/display: fix bug of accessing invalid memory

[Why]
A loop inside of build_evenly_distributed_points function that traverse through
the array of points become an infinite loop when m_GammaUpdates does not
get assigned to any value.

[How]
In DMColor, clear m_gammaIsValid bit just before writting all Zeromem for
m_GammaUpdates, to prevent calling build_evenly_distributed_points
before m_GammaUpdates gets assigned to some value.
Signed-off-by: NSu Sung Chung <Su.Chung@amd.com>
Reviewed-by: NAric Cyr <Aric.Cyr@amd.com>
Acked-by: NBhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/modules/color/color_gamma.c

@@ -1069,10 +1069,14 @@ static void build_evenly_distributed_points(
 	struct dividers dividers)
 {
 	struct gamma_pixel *p = points;
-	struct gamma_pixel *p_last = p + numberof_points - 1;
+	struct gamma_pixel *p_last;
 
 	uint32_t i = 0;
 
+	// This function should not gets called with 0 as a parameter
+	ASSERT(numberof_points > 0);
+	p_last = p + numberof_points - 1;
+
 	do {
 		struct fixed31_32 value = dc_fixpt_from_fraction(i,
 			numberof_points - 1);
@@ -1083,7 +1087,7 @@ static void build_evenly_distributed_points(
 
 		++p;
 		++i;
-	} while (i != numberof_points);
+	} while (i < numberof_points);
 
 	p->r = dc_fixpt_div(p_last->r, dividers.divider1);
 	p->g = dc_fixpt_div(p_last->g, dividers.divider1);