ARM: dts: add SDCC5 to Qualcomm MSM8660

The SDCC5 SD/MMC controller is used for a second uSD slot
on the APQ8060 Dragonboard. On most other systems it is just
dark silicon so define it and leave it as "disabled" in the core
SoC file.

Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>