kernel: userspace.c code cleanup

- Dumping error messages split from _k_object_validate(), to avoid spam
  in test cases that are expected to have failure result.

- _k_object_find() prototype moved to syscall_handler.h

- Clean up k_object_access() implementation to avoid double object
  lookup and use single validation function

- Added comments, minor whitespace changes

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
5 files changed