msm: Pull cache dumping out of the board file

The cache dumping device belongs in the devices file with
the rest of the platorm devices. Pull it out and add appropriate
definitions in headers for access. Also remove CONFIG_MSM_CACHE_DUMP
macros around the device and code since platform device matching
will do the proper thing if CONFIG_MSM_CACHE_DUMP is not defined.

Change-Id: I713378b36c166f611e723e4b1ee0d7bdd8bf6497
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>