doc: Various corrections to Kernel Primer

* Ensures all references to kernel functions are correctly
  tagged so they will auto-link to the API guide.

* Adds references to a few functions and macros that were
  omitted.

Change-Id: I26ccd9c29ea123db2807f2df4d05d574932c6849
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>