iommu/rockchip: Fix TLB flush of secondary IOMMUs

Due to the bug in current code, only first IOMMU has the TLB lines
flushed in rk_iommu_zap_lines. This patch fixes the inner loop to
execute for all IOMMUs and properly flush the TLB.

Signed-off-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>