diag: Add changes to support 64 bit

The diag driver is required to work in 32 bit as well as
64 bit mode. This includes running with a 64 bit kernel
and 32 bit userspace. Make changes to support both 32 and
64 bit operation.

Change-Id: Ib37269203ac2e38d887e8fd650fc407ff604f2ac
Signed-off-by: Dixon Peterson <dixonp@codeaurora.org>