ARM OMAP2+ GPMC: change get_gpmc_timing_reg output for DTS

DTS output was formatted to require additional work when copy-pasting into DTS.
Nano-second timings were replaced with interval of values that produce the same
number of clock ticks.

Signed-off-by: Robert ABEL <rabel@cit-ec.uni-bielefeld.de>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>