arch/powerpc: Add Power9 CPU type

The Power9 CPU was released by IBM in 2016. It is a 64-bit CPU
implementing ISA v3.0. It runs in big and little endian modes, and
supports VSX and AltiVec.

Power9 is supported as of GCC 6.1 and Binutils 2.26.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Yann E. MORIN <yann.morin.1998@free.fr>
[Arnout: remove 64-bit constraint]
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>

arch/Config.in.powerpc

@@ -139,6 +139,11 @@ config BR2_powerpc_power7
 config BR2_powerpc_power8
 	bool "power8"
 	select BR2_POWERPC_CPU_HAS_VSX
+config BR2_powerpc_power9
+	bool "power9"
+	select BR2_POWERPC_CPU_HAS_ALTIVEC
+	select BR2_POWERPC_CPU_HAS_VSX
+	select BR2_ARCH_NEEDS_GCC_AT_LEAST_6
 endchoice
 
 choice
@@ -216,6 +221,7 @@ config BR2_GCC_TARGET_CPU
 	default "power6"	if BR2_powerpc_power6
 	default "power7"	if BR2_powerpc_power7
 	default "power8"	if BR2_powerpc_power8
+	default "power9"	if BR2_powerpc_power9
 
 config BR2_READELF_ARCH_NAME
 	default "PowerPC"	if BR2_powerpc