checkpatch: warn on embedded function names

Embedded function names are less appropriate to use when refactoring can
cause function renaming.  Prefer the use of "%s", __func__ to embedded
function names.

Link: http://lkml.kernel.org/r/ac9631fdbac5af3507c5bfe88ad9064f0ed764ec.1483510416.git.joe@perches.com


Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>