clk: tegra: Fix the misnaming of nvenc from msenc

When adding the nvenc clock, it was partially named msenc in the code.
Since the msenc clock isn't present in Tegra210 and has been replaced by
the nvenc clock, its misleading to see it present. Therefore, properly
rename it.

Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>