soc: qcom: Add API to obtain pointer to dump addr

The API will be used by memory dump clients to obtain
the virtual address to their dump location. This is needed
if a client wants to dump out some custom information.

Change-Id: Ifb2c06456dc47c975a3159f98cd67d1ebff8935a
Signed-off-by: Satyajit Desai <sadesai@codeaurora.org>