kbuild: sparse needs CF not CHECKFLAGS

Documentation/sparse.txt tells to use:

    make C=2 CHECKFLAGS="-D__CHECK_ENDIAN__"

However, this still doesn't enable endian checks. The correct syntax is:

    make C=2 CF="-D__CHECK_ENDIAN__"

This documentation bug was introduced by the following commit:

    commit 1c7bafe7


    Author: Robert P. J. Day <rpjday@mindspring.com>
    Date:   Wed Sep 13 07:57:50 2006 -0400

	kbuild: clarify "make C=" build option

	Clarify the use of "make C=" in the top-level Makefile, and fix a
	typo in the Documentation file.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

This `typo' was not a typo, as `CF' had been introduced much earlier, by:

    commit 7b49bb9a


    Author: viro@ZenIV.linux.org.uk <viro@ZenIV.linux.org.uk>
    Date:   Fri Sep 9 21:14:35 2005 +0100

	[PATCH] kbuild: CF=<arguments> passes arguments to sparse

	Allows to add to sparse arguments without mutilating makefiles - just
	pass CF=<arguments> and they will be added to CHECKFLAGS.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>