video: fbdev: s1d13xxxfb: Fix kernel-doc and set but not used warnings

Fix following W=1 warnings:
- Fix set but not used variables that were used only for logging.
  Fixed by introducing no_printk() to trick compiler to think variables
  are used
- Fix kernel-doc warning by deleting an empty comment line

v3:
  - Fix grammar in commit message (Thomas)
v2:
  - Subject updated (Lee)

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Kristoffer Ericson <kristoffer.ericson@gmail.com>
Cc: Lee Jones <lee.jones@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201128224114.1033617-29-sam@ravnborg.org