arch: blackfin: uapi: be sure of "_UAPI" prefix for all guard macros

For all uapi headers, need use "_UAPI" prefix for its guard macro
(which will be stripped by "scripts/headers_installer.sh").

Also be sure that all files have their guard macros.

Also be sure that all "#endif" are followed with comments, and no '\t'
for guard macro

Signed-off-by: Chen Gang <gang.chen@asianux.com>