arm: docs: Move Arm documentation to Documentation/arch/

arm: docs: Move Arm documentation to Documentation/arch/

Architecture-specific documentation is being moved into Documentation/arch/
as a way of cleaning up the top-level documentation directory and making
the docs hierarchy more closely match the source hierarchy.  Move
Documentation/arm into arch/ (along with the Chinese equvalent
translations).

Cc: Maxime Coquelin <[email protected]>
Cc: Chen-Yu Tsai <[email protected]>
Cc: Jernej Skrabec <[email protected]>
Cc: Samuel Holland <[email protected]>
Cc: Krzysztof Kozlowski <[email protected]>
Cc: Alim Akhtar <[email protected]>
Cc: Alex Shi <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Acked-by: Alexandre TORGUE <[email protected]>
Reviewed-by: Yanteng Si <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>