hw/display/artist: Fix bug in coordinate extraction in artist_vram_read() and artist_...

hw/display/artist: Fix bug in coordinate extraction in artist_vram_read() and artist_vram_write()

The CDE desktop on HP-UX 10 shows wrongly rendered pixels when the local screen
menu is closed. This bug was introduced by commit c7050f3f167b
("hw/display/artist: Refactor x/y coordination extraction") which converted the
coordinate extraction in artist_vram_read() and artist_vram_write() to use the
ADDR_TO_X and ADDR_TO_Y macros, but forgot to right-shift the address by 2 as
it was done before.

Signed-off-by: Helge Deller <deller@gmx.de>
Fixes: c7050f3f167b ("hw/display/artist: Refactor x/y coordination extraction")
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Sven Schnelle <svens@stackframe.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <YK1aPb8keur9W7h2@ls3530>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>