ARM: davinci_all_defconfig: set CONFIG_BACKLIGHT_PWM=m

The da850-evm came with an LCD with a backlight tied to a pwm. This
enables CONFIG_BACKLIGHT_PWM as a module so the PWM backlight can be
used to maintain brightness control of the backlight.
Signed-off-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>

arch/arm/configs/davinci_all_defconfig

@@ -153,6 +153,7 @@ CONFIG_TINYDRM_ST7586=m
 CONFIG_FB=y
 CONFIG_FIRMWARE_EDID=y
 CONFIG_FB_DA8XX=y
+CONFIG_BACKLIGHT_PWM=m
 CONFIG_FRAMEBUFFER_CONSOLE=y
 CONFIG_LOGO=y
 CONFIG_SOUND=m