doxygen: change comment style to match javadoc

The change replaces multiple asterisks to ** at
the beginning of comments and adds a space before
the asterisks at the beginning of lines.

Change-Id: I7656bde3bf4d9a31e38941e43b580520432dabc1
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
305 files changed