coresight: change magic number for memory dump v2

Memory dump v2 format uses magic number that is different from
what is used with earlier version. Add support for this change
so that the TMC ramdump can be correctly parsed.

Change-Id: Ib7f5478812e59a44c609fc433e8c742fe30488a9
Signed-off-by: Aparna Das <adas@codeaurora.org>