Drop SRC_ROOT from mainboard Makefile.incs

It's not used, and not needed.

Change-Id: Ifca92f3606ac58fc26e09676488c3add5d84ae79
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/2548
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/mainboard/emulation/qemu-armv7/Makefile.inc

@@ -26,5 +26,3 @@ ramstage-y += timer.c
 bootblock-$(CONFIG_EARLY_CONSOLE) += uart.c
 romstage-$(CONFIG_EARLY_CONSOLE) += uart.c
 ramstage-y += uart.c
-
-SRC_ROOT = $(src)/mainboard/emulation/qemu-armv7a

src/mainboard/google/butterfly/Makefile.inc

@@ -23,5 +23,3 @@ romstage-$(CONFIG_CHROMEOS) += chromeos.c
 ramstage-$(CONFIG_CHROMEOS) += chromeos.c
 
 smm-$(CONFIG_HAVE_SMI_HANDLER) += mainboard_smi.c
-
-SRC_ROOT = $(src)/mainboard/google/butterfly

src/mainboard/google/link/Makefile.inc

@@ -27,14 +27,12 @@ ramstage-$(CONFIG_MAINBOARD_DO_NATIVE_VGA_INIT) += i915io.c
 smm-$(CONFIG_HAVE_SMI_HANDLER) += mainboard_smi.c
 SPD_BIN = $(obj)/spd.bin
 
-SRC_ROOT = $(src)/mainboard/google/link
-
 # Order of names in SPD_SOURCES is important!
 SPD_SOURCES = elpida_4Gb_1600_x16
 SPD_SOURCES += samsung_4Gb_1600_1.35v_x16
 SPD_SOURCES += micron_4Gb_1600_1.35v_x16
 
-SPD_DEPS := $(foreach f, $(SPD_SOURCES), $(SRC_ROOT)/$(f).spd.hex)
+SPD_DEPS := $(foreach f, $(SPD_SOURCES), src/mainboard/$(MAINBOARDDIR)/$(f).spd.hex)
 
 # Include spd rom data
 $(SPD_BIN): $(SPD_DEPS)

src/mainboard/google/parrot/Makefile.inc

@@ -21,5 +21,3 @@ ramstage-y += ec.c
 
 romstage-$(CONFIG_CHROMEOS) += chromeos.c
 ramstage-$(CONFIG_CHROMEOS) += chromeos.c
-
-SRC_ROOT = $(src)/mainboard/google/parrot

src/mainboard/google/snow/Makefile.inc

@@ -24,9 +24,3 @@ romstage-y += romstage.c
 # ramstage-y += ec.c
 ramstage-y += ramstage.c
 ramstage-y += chromeos.c
-
-# romstage-$(CONFIG_CHROMEOS) += chromeos.c
-
-# FIXME: we should do something similar to x86 platforms for Snow SPDs
-
-SRC_ROOT = $(src)/mainboard/google/snow