soc: qcom: bring all qcom drivers into a submenu

As the number of qcom drivers increase, entries in SOC menu looks
scattered with other SOC drivers. Make a submenu for Qcom drivers
to make it visibly clear while selecting qcom SOC specific drivers.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>