ARM: configs: fix duplicate entry in multi_v7

Two of the recent patches each added support for CPU_FREQ, which
causes a kconfig warning:

arch/arm/configs/multi_v7_defconfig:443:warning: override: reassigning to symbol CPU_FREQ

This removes one of the two in order to avoid the warning.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/configs/multi_v7_defconfig

@@ -439,5 +439,4 @@ CONFIG_DEBUG_FS=y
 CONFIG_MAGIC_SYSRQ=y
 CONFIG_LOCKUP_DETECTOR=y
 CONFIG_CRYPTO_DEV_TEGRA_AES=y
-CONFIG_CPU_FREQ=y
 CONFIG_GENERIC_CPUFREQ_CPU0=y