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 <[email protected]>
[swarren, extracted from a larger patch by Tom]
Signed-off-by: Stephen Warren <[email protected]>
Reviewed-by: Thierry Reding <[email protected]>
Tested-by: Thierry Reding <[email protected]>
Acked-by: Thierry Reding <[email protected]>
Signed-off-by: Tom Warren <[email protected]>