ARM: msm: Add support for MSM8974 SoC

Add support for the Snapdragon 800 MSM8974 SoC, used on the Dragonboard
and others. Board support added in separate patch.

Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>
Acked-by: Kumar Gala <galak@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>
[olof: split off SoC support in separate patch]
Signed-off-by: Olof Johansson <olof@lixom.net>