kbuild: use relative path to -I

Using a relative path has the advantage that when the kernel source
tree is moved the relevant .o files will not be rebuild just because
the path to the kernel src has changed.
This also got rid of a user of TOPDIR - which has been deprecated for a long time now.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

arch/ppc/boot/lib/Makefile

@@ -3,7 +3,7 @@
 #
 
 CFLAGS_kbd.o	:= -Idrivers/char
-CFLAGS_vreset.o := -I$(srctree)/arch/ppc/boot/include
+CFLAGS_vreset.o := -Iarch/ppc/boot/include
 
 zlib  := infblock.c infcodes.c inffast.c inflate.c inftrees.c infutil.c
 	 

arch/sparc/math-emu/Makefile

@@ -5,4 +5,4 @@
 obj-y    := math.o
 
 EXTRA_AFLAGS := -ansi
-EXTRA_CFLAGS = -I. -I$(TOPDIR)/include/math-emu -w
+EXTRA_CFLAGS = -I. -Iinclude/math-emu -w

drivers/media/video/bt8xx/Makefile

@@ -9,4 +9,4 @@ bttv-objs      :=      bttv-driver.o bttv-cards.o bttv-if.o \
 obj-$(CONFIG_VIDEO_BT848) += bttv.o
 
 EXTRA_CFLAGS += -I$(src)/..
-EXTRA_CFLAGS += -I$(srctree)/drivers/media/dvb/dvb-core
+EXTRA_CFLAGS += -Idrivers/media/dvb/dvb-core