clk: tegra: Fix PLLE programming

PLLE has M, N and P divider shift and width parameters that differ from
the defaults. Furthermore, when clearing the M, N and P divider fields
the corresponding masks were never shifted, thereby clearing only the
lowest bits of the register. This lead to a situation where the PLLE
programming would only work if the register hadn't been touched before.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>