drm/amd/display: Add Null check for DPP resource

stable inclusion
from stable-v6.6.3
commit 17117871bf0d6792f7aacec0f57cdc63fc01042a
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8LBQP

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=17117871bf0d6792f7aacec0f57cdc63fc01042a



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commit e186400685d8a9287388a8535e2399bc673bfe95 upstream.

[what and why]
Check whether dpp resource pointer is null in advance and return early
if so.

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Reviewed-by: Martin Leung <martin.leung@amd.com>
Signed-off-by: Gabe Teeger <gabe.teeger@amd.com>
Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>