backlight/bd6107: Rename struct bd6107_platform_data.fbdev to 'dev'

Rename struct bd6107_platform_data.fbdev to 'dev', as it stores a
pointer to the Linux platform device; not the fbdev device. Makes
the code easier to understand.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Lee Jones <lee@kernel.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jingoo Han <jingoohan1@gmail.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230613110953.24176-3-tzimmermann@suse.de