make clean, make mrproper, make distclean

from the Makefile:

###
# Cleaning is done on three levels.
# make clean          Delete most generated files;
#                              Leave enough to build external modules
#                              (remove all the object *.o and kernel object files *.ko
#                               and a few other things)
# make mrproper   Delete the current configuration, and all generated files
# make distclean     Remove editor backup files, patch leftover files and the like
#                               (plus remove your config file, the dependency files,
#                                and everything else that make config creates.)