build: define CPU only when arch/${ARCH}/cpu/${CPU} exists

The directory arch/${ARCH}/cpu/${CPU} does not exist
in avr32, blackfin, microblaze, nios2, openrisc, sandbox, x86.

These architectures have only one CPU type.
Defining CPU should not be required for such architectures.

This commit allows cpu field (= the 3rd field of boards.cfg)
to be kept blank.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Andreas Bießmann <andreas.devel@googlemail.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Sonic Zhang <sonic.zhang@analog.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Thomas Chou <thomas@wytron.com.tw>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>

config.mk

@@ -24,10 +24,7 @@ OBJCOPYFLAGS :=
 # so calculate CPUDIR before including ARCH/SOC/CPU config.mk files.
 # Check if arch/$ARCH/cpu/$CPU exists, otherwise assume arch/$ARCH/cpu contains
 # CPU-specific code.
-CPUDIR=arch/$(ARCH)/cpu/$(CPU)
-ifneq ($(srctree)/$(CPUDIR),$(wildcard $(srctree)/$(CPUDIR)))
-CPUDIR=arch/$(ARCH)/cpu
-endif
+CPUDIR=arch/$(ARCH)/cpu$(if $(CPU),/$(CPU),)
 
 sinclude $(srctree)/arch/$(ARCH)/config.mk	# include architecture dependend rules
 sinclude $(srctree)/$(CPUDIR)/config.mk		# include  CPU	specific rules

drivers/sound/sandbox.c

@@ -5,7 +5,7 @@
  */
 
 #include <common.h>
-#include <asm/arch/sound.h>
+#include <asm/sound.h>
 #include <asm/sdl.h>
 
 int sound_play(uint32_t msec, uint32_t frequency)

mkconfig

@@ -55,6 +55,11 @@ CONFIG_NAME="${7%_config}"
 arch="$2"
 cpu=`echo $3 | awk 'BEGIN {FS = ":"} ; {print $1}'`
 spl_cpu=`echo $3 | awk 'BEGIN {FS = ":"} ; {print $2}'`
+
+if [ "$cpu" = "-" ] ; then
+	cpu=
+fi
+
 if [ "$6" = "<none>" ] ; then
 	board=
 elif [ "$6" = "-" ] ; then
@@ -114,10 +119,10 @@ fi
 
 rm -f asm/arch
 
-if [ -z "${soc}" ] ; then
-	ln -s ${LNPREFIX}arch-${cpu} asm/arch
-else
+if [ "${soc}" ] ; then
 	ln -s ${LNPREFIX}arch-${soc} asm/arch
+elif [ "${cpu}" ] ; then
+	ln -s ${LNPREFIX}arch-${cpu} asm/arch
 fi
 
 if [ -z "$KBUILD_SRC" ] ; then