drivers/video/igafb.c: introduce lost 'return'

If iga_init() fails, code releases resources and continues to use it.  It
seems that after releasing resources 'return' should be.

Signed-off-by: Kulikov Vasiliy <segooon@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>