[PATCH] kbuild: more Makefile cleanups

This adds the remaining changes which should have been part of the
review process.

 - the define command is inappropriate (it's primarily for rule
   definitions)
 - execute commands in the current dir as all other commands
 - .*.tmp (but not .*.null) files are also removed up by "make clean"
 - printf has other side effects, just use "echo -e"
 - proper quoting
 - proper indentation

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>