imx: mx6: use simpler runtime cpu dection macros

Use simpler runtime cpu dection macros.
i.MX6DL and i.MX6SOLO work the same, so use is_mx6sdl.

Signed-off-by: Peng Fan <van.freenix@gmail.com>
Cc: Stefano Babic <sbabic@denx.de>
3 files changed