clk: tegra: dfll: Fix a potential Oop in remove()

[ Upstream commit d39eca54 ]

If tegra_dfll_unregister() fails then "soc" is an error pointer.  We
should just return instead of dereferencing it.

Fixes: 1752c9ee ("clk: tegra: dfll: Fix drvdata overwriting issue")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>