cleanup: Use quote include instead of system include

When the header file is located in the same directory as the source
file it is better to use a relative quote-include, e.g.

than a system include like

Avoiding the use of system includes in these cases is beneficial
because;

* The source code will be easier to build because there will be fewer
system include paths.

* It is easier for a user to determine where a quote-include header
  file is located than where a system include is located.

* You are less likely to encounter aliasing issues if the list of
  system include paths is minimized.

Authors:
Anas Nashif
Sebastian Bøe

Signed-off-by: Sebastian Boe <sebastian.boe@nordicsemi.no>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>