ARM: omap2plus_defconfig: enable ECAP and EHRPWM

Many of AM335x and AM437x hook backlight to
one of these two devices. By enabling their
drivers we make sure pwm-backlight can do
its thing.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>