backlight: omap1: Replace FB_BLANK_ states with simple on/off

The backlight is on for fb_blank eq FB_BLANK_UNBLANK, or off for
any other value in fb_blank. But the field fb_blank in struct
backlight_properties is deprecated and should not be used any
longer.

Replace the test for fb_blank in omap's backlight code with a
simple boolean parameter and push the test into the update_status
helper. Instead of reading fb_blank directly, decode the backlight
device's status with backlight_is_blank().

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240319093915.31778-4-tzimmermann@suse.de


Signed-off-by: Lee Jones <lee@kernel.org>