drm/nouveau: fix dma_address check for CPU/GPU sync

stable inclusion
from stable-5.10.48
commit 45ca6df5df11da7f19c85591e093479d5c60262f
bugzilla: 173268 https://gitee.com/openeuler/kernel/issues/I4DD1K

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=45ca6df5df11da7f19c85591e093479d5c60262f



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[ Upstream commit d3300991 ]

AGP for example doesn't have a dma_address array.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210614110517.1624-1-christian.koenig@amd.com


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>