imx: mx6: display max cpu frequency in print_cpuinfo()

imx: mx6: display max cpu frequency in print_cpuinfo()

Display the max CPU frequency as well as the current running CPU frequency
if the max CPU frequency is available and differs from the current CPU
frequency.

Before:
CPU:   Freescale i.MX6Q rev1.2 at 792 MHz

After - using an 800MHz IMX6DL (running at its max)
CPU:   Freescale i.MX6DL rev1.1 at 792 MHz

After - using a 1GHz IMX6Q (not running at its max):
CPU:   Freescale i.MX6Q rev1.2 996 MHz (running at 792 MHz)

Cc: Stefan Roese <[email protected]>
Cc: Eric Nelson <[email protected]>
Cc: Heiko Schocher <[email protected]>
Cc: Nikita Kiryanov <[email protected]>
Cc: Jon Nettleton <[email protected]>
Cc: Jason Liu <[email protected]>
Cc: Ye Li <[email protected]>
Cc: Fabio Estevam <[email protected]>
Cc: Christian Gmeiner <[email protected]>
Cc: Markus Niebel <[email protected]>
Cc: Peng Fan <[email protected]>
Tested-by: Nikolay Dimitrov <[email protected]>
Signed-off-by: Tim Harvey <[email protected]>