omap2plus_defconfig: enable devfreq

Signed-off-by: Nishanth Menon <nm@ti.com>
PM / devfreq: add omap_coproc driver

UNDER DEVEL
play with:/sys/devices/platform/iva.0/stat_busy_time
and /sys/devices/platform/pvrsrvkm.0/stat_busy_time
to input "system behavior"

TODO: This patch was first created in 2012, needs an update to work in
2014. will do that later.

Signed-off-by: Nishanth Menon <nm@ti.com>