util/kconfig: Uprev to Linux 5.13's kconfig

This was originally several commits that had to be squashed into one
because the intermediate states weren't able to build coreboot:

 - one to remove everything that wasn't our own code, leaving only
   regex.[ch], toada.c, description.md and Makefile.inc.
 - one to copy in Linux 5.13's scripts/kconfig and adapt Makefile.inc
   to make the original Makefile work again.
 - adapt abuild to use olddefconfig, simplifying matters.
 - apply patches in util/kconfig/patches.
 - Some more adaptations to the libpayload build system.

The patches are now in util/kconfig/patches/, reverse applying them
should lead to a util/kconfig/ tree that contains exactly the Linux
version + our own 5 files.

Change-Id: Ia0e8fe4e9022b278f34ab113a433ef4d45e5c355
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37152
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

payloads/libpayload/Makefile.payload

@@ -119,6 +119,7 @@ $(obj)/%.S.o: %.S $(LIBPAYLOAD_CONFIG_H) $(DEFAULT_DEPS)
 
 LIBPAYLOAD_OPTS := obj="$(LIBPAYLOAD_OBJ)"
 LIBPAYLOAD_OPTS += DOTCONFIG="$(LIBPAYLOAD_DOTCONFIG)"
+LIBPAYLOAD_OPTS += CONFIG_=CONFIG_LP_
 LIBPAYLOAD_OPTS += $(if $(CCACHE),CONFIG_LP_CCACHE=y)
 
 defconfig: lp-defconfig