fbgrab: fix installed but not shipped warnings

WARNING: QA Issue: fbgrab: Files/directories were installed but not shipped
  /usr/man
  /usr/man/man1
  /usr/man/man1/fbgrab.1.gz

Signed-off-by: Jonathan Liu <net147@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>