ARM: imx: Place "Cortex-A/Cortex-M" comment in the correct location

The menu comment "Cortex-A/Cortex-M asymmetric multiprocessing platforms"
appears when running:

make imx_v4_v5_defconfig
make menuconfig

System Type --->
[*] Freescale i.MX family  --->

This is not correct as imx_v4_v5_defconfig does not select any Cortex-A
or Cortex-M platforms.

Move the comment under the correct symbol ifdefery to fix this problem.

Fixes: 8064887e ("ARM: vf610: enable Cortex-M4 configuration on Vybrid SoC")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>