staging: sm750fb: print error message with actual value

This patch will update error message, so it is same as error message in
another function.

Signed-off-by: Matej Dujava <mdujava@kocurkovo.cz>
Link: https://lore.kernel.org/r/1588277366-19354-4-git-send-email-mdujava@kocurkovo.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>