diag: Change format used for printing pointers

Currently, when printing a pointer address the format does
not take advantage of using the pointer conversion specifier.
Make changes to use the pointer conversion specifier.

Also, the read and write of the file_operations structure
is not returning the correct data type. Make changes so these
functions return the appropriate data type.

Change-Id: I921a4db21ad833439f5bf8994fa42974e2d70c96
Signed-off-by: Dixon Peterson <dixonp@codeaurora.org>