imx: mx7: drop select CPU_V7 for board target

drop select CPU_V7 for board target, since ARCH_MX7 selects CPU_V7.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>

arch/arm/cpu/armv7/mx7/Kconfig

@@ -13,7 +13,6 @@ choice
 
 config TARGET_MX7DSABRESD
 	bool "mx7dsabresd"
-	select CPU_V7
 	select DM
 	select DM_THERMAL