doc: Various corrections to doxygen info for Kernel APIs

Most kernel APIs are now ready for inclusion in the API guide.
The APIs largely follow a standard template to provide users
of the API guide with a consistent look-and-feel.

Change-Id: Ib682c31f912e19f5f6d8545d74c5f675b1741058
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>