devres: Improve devm_kasprintf()/kvasprintf() support

devres: Improve devm_kasprintf()/kvasprintf() support

  - Add devm_kasprintf()/kvasprintf(), introduced by commit
    75f2a4ead5d5890ada9c2663a70fb58613c0d9f2 ("devres: Add
    devm_kasprintf and devm_kvasprintf API"), to
    Documentation/driver-model/devres.txt,
  - Improve kernel doc: the string is not an existing formatted string,
    but is formatted into the newly-allocated buffer,
  - Add a __printf() annotation to devm_kasprintf(), so the compiler
    will verify the format string argument types.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit bef59c5024be687ef4f228915af9961307a779ab)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Conflicts:
	Documentation/driver-model/devres.txt
	drivers/base/devres.c