drm/amd/display: drop redundant memset() in get_available_dsc_slices()

get_available_dsc_slices() returns the number of indices set, and all of
the users of get_available_dsc_slices() don't cross the returned bound
when iterating over available_slices[]. So, the memset() in
get_available_dsc_slices() is redundant and can be dropped.

Fixes: 97bda032 ("drm/amd/display: Add DSC support for Navi (v2)")
Reported-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c

@@ -645,8 +645,6 @@ static int get_available_dsc_slices(union dsc_enc_slice_caps slice_caps, int *av
 {
 	int idx = 0;
 
-	memset(available_slices, -1, MIN_AVAILABLE_SLICES_SIZE);
-
 	if (slice_caps.bits.NUM_SLICES_1)
 		available_slices[idx++] = 1;