ARM: tegra: deduplicate MASK_BITS_xxx clock mux enum

ARM: tegra: deduplicate MASK_BITS_xxx clock mux enum

The enum used to define the set of register bits used to represent a
clock's input mux, MUX_BITS_*, is defined separately for each SoC at
present. Move this definition to a common location to ease fixing up
some issues with the definition, and the code that uses it.

Signed-off-by: Tom Warren <twarren@nvidia.com>
[swarren, extracted from a larger patch by Tom]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>