package/librtas: only show comment on supported architectures

librtas is only available for PPC and PPC64, so only show the comment
about the (e)glibc dependency for those archs.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Sam Bobroff <sam.bobroff@au1.ibm.com>
Reviewed-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/librtas/Config.in

@@ -10,4 +10,5 @@ config BR2_PACKAGE_LIBRTAS
 	  http://librtas.sourceforge.net/
 
 comment "librtas needs an (e)glibc toolchain"
+	depends on BR2_powerpc || BR2_powerpc64 || BR2_powerpc64le
 	depends on !BR2_TOOLCHAIN_USES_GLIBC