arm64: Enable TIMER_IMX_SYS_CTR for ARCH_MXC platforms

ARCH_MXC platforms needs system counter as broadcast timer
to support cpuidle, enable it by default.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/Kconfig.platforms

@@ -173,6 +173,7 @@ config ARCH_MXC
 	select PM
 	select PM_GENERIC_DOMAINS
 	select SOC_BUS
+	select TIMER_IMX_SYS_CTR
 	help
 	  This enables support for the ARMv8 based SoCs in the
 	  NXP i.MX family.