kbuild: remove -I$(srctree)/tools/include from scripts/Makefile

I do not like to add an extra include path for every tool with no
good reason. This should be specified per file.

This line was added by commit 6520fe55 ("x86, realmode: 16-bit
real-mode code support for relocs tool"), which did not touch
anything else in scripts/. I see no reason to add this.

Also, remove the comment about kallsyms because we do not have any
for the rest of programs.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/Makefile

@@ -2,10 +2,6 @@
 ###
 # scripts contains sources for various helper programs used throughout
 # the kernel for the build process.
-# ---------------------------------------------------------------------------
-# kallsyms:      Find all symbols in vmlinux
-
-HOST_EXTRACFLAGS += -I$(srctree)/tools/include
 
 always-$(CONFIG_BUILD_BIN2C)			+= bin2c
 always-$(CONFIG_KALLSYMS)			+= kallsyms