ARM: pxa: centro and treo680 need palm27x

The two platforms are part of the palm27x family and use the same
code. Select the palm27x symbol to make sure they can be built
standalone.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>

arch/arm/mach-pxa/Kconfig

@@ -427,6 +427,7 @@ config MACH_CENTRO
 	bool "Palm Centro 685 (GSM)"
 	default y
 	depends on ARCH_PXA_PALM
+	select MACH_PALM27X
 	select PXA27x
 	select IWMMXT
 	select PALM_TREO
@@ -438,6 +439,7 @@ config MACH_TREO680
 	bool "Palm Treo 680"
 	default y
 	depends on ARCH_PXA_PALM
+	select MACH_PALM27X
 	select PXA27x
 	select IWMMXT
 	select PALM_TREO