kconfig: Get rid of the P() macro in headers

This was originally meant for dlopen()ing a potential kconfig shared
library. The unused dlopen code has already been removed in commit
5a6f8d2b (kconfig: nuke LKC_DIRECT_LINK cruft), so let's remove the
rest. The lkc_proto.h change was made with the following sed script:

  sed -r 's/^P\(([^,]*), *([^,]*), *(.*)\);/\2 \1\3;/'

Plus some manual adjustments.

Signed-off-by: Michal Marek <mmarek@suse.cz>