drivers: soc: Provide separate api for ramdump registration

Currently all clients registering to dump table framework are
implicitly registered for minidump framework. Provide an api to
exclusively register for ramdumps.

Change-Id: I0e8eee366d898699d0354c9abb326822ba452ef0
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>