platform/x86/intel/pmt: allow user offset for PMT callbacks

platform/x86/intel/pmt: allow user offset for PMT callbacks

Usage of the telem sysfs file allows for partial reads at an offset.
The current callback method returns the buffer starting from offset 0
only.

Include the requested offset in the callback and update the necessary
address calculations with the offset.

Note: offset addition is moved from the caller to the local usage. For
non-callback usage this is unchanged behavior.

Fixes: e92affc74cd8 ("platform/x86/intel/vsec: Add PMT read callbacks")
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Link: https://lore.kernel.org/r/20241114130358.2467787-2-michael.j.ruhl@intel.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>