ARM: S5P64XX: Remove redundant selection PLAT_S5P.

This patch removes redundant selection PLAT_S5P in the CPU_S5P64XX config.
Because PLAT_S5P is selected if select ARCH_S5P64XX in the plat-s5p/Kconfig.
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/mach-s5p6442/Kconfig

@@ -11,7 +11,6 @@ if ARCH_S5P6442
 
 config CPU_S5P6442
 	bool
-	select PLAT_S5P
 	select S3C_PL330_DMA
 	help
 	  Enable S5P6442 CPU support

arch/arm/mach-s5p64x0/Kconfig

@@ -9,14 +9,12 @@ if ARCH_S5P64X0
 
 config CPU_S5P6440
 	bool
-	select PLAT_S5P
 	select S3C_PL330_DMA
 	help
 	  Enable S5P6440 CPU support
 
 config CPU_S5P6450
 	bool
-	select PLAT_S5P
 	select S3C_PL330_DMA
 	help
 	  Enable S5P6450 CPU support