libpayload: Make Kconfig bools use IS_ENABLED()

This will make the code work with the different styles
of Kconfig (emit unset bools vs don't emit unset bools)

Roughly, the patch does this, and a little bit of fixing up:

perl -pi -e 's,ifdef (CONFIG_LP_.+?)\b,if IS_ENABLED\($1\),g' `find . -name *.[ch]`
perl -pi -e 's,ifndef (CONFIG_LP_.+?)\b,if !IS_ENABLED\($1\),g' `find . -name *.[ch]`

Change-Id: Ib8a839b056a1f806a8597052e1b571ea3d18a79f
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: http://review.coreboot.org/10711
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

payloads/libpayload/libcbfs/cbfs.c

@@ -31,7 +31,7 @@
 
 #ifdef LIBPAYLOAD
 # include <libpayload-config.h>
-# ifdef CONFIG_LP_LZMA
+# if IS_ENABLED(CONFIG_LP_LZMA)
 #  include <lzma.h>
 #  define CBFS_CORE_WITH_LZMA
 # endif