linux: Fix powerpc64le defconfig selection

The default defconfig target for the 64 bit powerpc kernel is
ppc64_defconfig, the big endian configuration.

When building for powerpc64le users want the little endian kernel as
they can't boot LE userspace on a BE kernel.

Fix up the defconfig used in this case. This will avoid the following
autobuilder failure:

 VDSO32A arch/powerpc/kernel/vdso32/sigtramp.o
 cc1: error: ‘-m32’ not supported in this configuratioin
 make[4]: *** [arch/powerpc/kernel/vdso32/Makefile:49: arch/powerpc/kernel/vdso32/sigtramp.o] Error 1

 http://autobuild.buildroot.net/results/dd76d53bab56470c0b83e296872d7bb90f9e8296/

Note that the failure indicates the toolchain is configured to disable
the 32 bit target, causing the kernel to fail when building the 32 bit
VDSO. This is only a problem on the BE kernel as the LE kernel disables
CONFIG_COMPAT, aka 32 bit userspace support, by default.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

linux/linux.mk

@@ -307,7 +307,11 @@ endif
 ifeq ($(BR2_LINUX_KERNEL_USE_DEFCONFIG),y)
 LINUX_KCONFIG_DEFCONFIG = $(call qstrip,$(BR2_LINUX_KERNEL_DEFCONFIG))_defconfig
 else ifeq ($(BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG),y)
+ifeq ($(BR2_powerpc64le),y)
+LINUX_KCONFIG_DEFCONFIG = ppc64le_defconfig
+else
 LINUX_KCONFIG_DEFCONFIG = defconfig
+endif
 else ifeq ($(BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG),y)
 LINUX_KCONFIG_FILE = $(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE))
 endif