viafb: fix sparse warnings

viafb: fix sparse warnings

Fix this sparse warnings:

  drivers/video/via/viafbdev.c:871:3: warning: returning void-valued expression
  drivers/video/via/viafbdev.c:938:3: warning: returning void-valued expression
  drivers/video/via/viafbdev.c:995:3: warning: returning void-valued expression

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>