accel/amdxdna: Clear sva pointer after unbind

accel/amdxdna: Clear sva pointer after unbind

Add client->sva = NULL after the unbind makes it consistent with how
amdxdna_sva_fini() already clears the pointer after unbinding. The
IS_ERR_OR_NULL guard in sva_fini will then correctly skip the second
unbind.

Fixes: 3cc5d7a59519 ("accel/amdxdna: Add carveout memory support for non-IOMMU systems")
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260604202815.2425882-1-lizhi.hou@amd.com