Merge remote-tracking branch 'remotes/kraxel/tags/vga-20171017-pull-request' into...

cirrus: bugfixes, with some vga cleanups.

# gpg: Signature made Tue 17 Oct 2017 09:24:37 BST
# gpg:                using RSA key 0x4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/vga-20171017-pull-request:
  cirrus: fix oob access in mode4and5 write functions
  vga: add ram_addr_t cast
  vga: handle cirrus vbe mode wraparounds.
  vga: drop line_offset variable

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>