clk: tegra: tegra124-emc: fix device leak on set_rate()

clk: tegra: tegra124-emc: fix device leak on set_rate()

Make sure to drop the reference taken when looking up the EMC device and
its driver data on first set_rate().

Note that holding a reference to a device does not prevent its driver
data from going away so there is no point in keeping the reference.

Fixes: 2db04f16b589 ("clk: tegra: Add EMC clock driver")
Fixes: 6d6ef58c2470 ("clk: tegra: tegra124-emc: Fix missing put_device() call in emc_ensure_emc_driver")
Cc: stable@vger.kernel.org	# 4.2: 6d6ef58c2470
Cc: Mikko Perttunen <mperttunen@nvidia.com>
Cc: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>