arch/Config.in.powerpc: VSX implies altivec

As spotted by Yann E. Morin in
https://patchwork.ozlabs.org/project/buildroot/patch/20220823212219.5066-1-fontaine.fabrice@gmail.com,
VSX is an extension to AltiVec:
https://en.wikipedia.org/wiki/AltiVec#VSX_(Vector_Scalar_Extension)

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>

arch/Config.in.powerpc

@@ -3,6 +3,7 @@ config BR2_POWERPC_CPU_HAS_ALTIVEC
 
 config BR2_POWERPC_CPU_HAS_VSX
 	bool
+	select BR2_POWERPC_CPU_HAS_ALTIVEC
 
 config BR2_POWERPC_CPU_HAS_SPE
 	bool
@@ -135,11 +136,9 @@ config BR2_powerpc_power6
 	select BR2_POWERPC_CPU_HAS_ALTIVEC
 config BR2_powerpc_power7
 	bool "power7"
-	select BR2_POWERPC_CPU_HAS_ALTIVEC
 	select BR2_POWERPC_CPU_HAS_VSX
 config BR2_powerpc_power8
 	bool "power8"
-	select BR2_POWERPC_CPU_HAS_ALTIVEC
 	select BR2_POWERPC_CPU_HAS_VSX
 endchoice