drm/amd/display: Guard against invalid RPTR/WPTR being set

stable inclusion
from stable-v6.6.3
commit 5a4d4bf6e3549a2b537c6cfe4a4e90468ad97367
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=5a4d4bf6e3549a2b537c6cfe4a4e90468ad97367



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commit 1ffa8602e39b89469dc703ebab7a7e44c33da0f7 upstream.

[WHY]
HW can return invalid values on register read, guard against these being
set and causing us to access memory out of range and page fault.

[HOW]
Guard at sync_inbox1 and guard at pushing commands.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Hansen Dsouza <hansen.dsouza@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@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>