Switch to GCC6 for Firenze and Mambo platforms

While hostboot is not yet ready for GCC6, although there is a pull request
for it: https://github.com/open-power/hostboot/pull/62 , other platforms
that don't build hostboot (Firenze, mambo simulator targets) can move to
GCC6 now.

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/openpower/configs/firenze_defconfig b/openpower/configs/firenze_defconfig
index 76b504c..9896809 100644
--- a/openpower/configs/firenze_defconfig
+++ b/openpower/configs/firenze_defconfig
@@ -3,6 +3,7 @@
 BR2_OPENPOWER_PLATFORM=y
 BR2_OPENPOWER_POWER8=y
 
+BR2_GCC_VERSION_6_X=y
 BR2_BINUTILS_EXTRA_CONFIG_OPTIONS="--enable-targets=powerpc64-linux"
 BR2_EXTRA_GCC_CONFIG_OPTIONS="--enable-targets=powerpc64-linux"
 
diff --git a/openpower/configs/openpower_mambo_defconfig b/openpower/configs/openpower_mambo_defconfig
index 0b6e3de..ed835f1 100644
--- a/openpower/configs/openpower_mambo_defconfig
+++ b/openpower/configs/openpower_mambo_defconfig
@@ -4,6 +4,7 @@
 BR2_OPENPOWER_POWER8=y
 
 BR2_KERNEL_HEADERS_4_4=y
+BR2_GCC_VERSION_6_X=y
 BR2_BINUTILS_VERSION_2_26_X=y
 BR2_BINUTILS_EXTRA_CONFIG_OPTIONS="--enable-targets=powerpc64-linux"
 BR2_EXTRA_GCC_CONFIG_OPTIONS="--enable-targets=powerpc64-linux"
diff --git a/openpower/configs/openpower_p9_mambo_defconfig b/openpower/configs/openpower_p9_mambo_defconfig
index 8b10d86..c86c3fd 100644
--- a/openpower/configs/openpower_p9_mambo_defconfig
+++ b/openpower/configs/openpower_p9_mambo_defconfig
@@ -1,6 +1,7 @@
 BR2_powerpc64le=y
 BR2_powerpc_power8=y
 BR2_KERNEL_HEADERS_4_4=y
+BR2_GCC_VERSION_6_X=y
 BR2_BINUTILS_VERSION_2_26_X=y
 BR2_BINUTILS_EXTRA_CONFIG_OPTIONS="--enable-targets=powerpc64-linux"
 BR2_EXTRA_GCC_CONFIG_OPTIONS="--enable-targets=powerpc64-linux"