Fix hardware accelerated video to video copy on Cirrus VGA (Brian Kress)

Fix hardware accelerated video to video copy on Cirrus VGA (Brian Kress)

cirrus_do_copy() in hw/cirrus_vga.c seems to make some incorrect assumptions
about video memory layout.  It tries to convert addresses to coordinates
assuming that one row of data is (width * depth) bytes long.  The correct way
seems to be to use the pitch fields in the CirrusVGAState structure instead.

Without this patch, I get lots of screen corruption when I try to drag a window
under X as it's passing the wrong coordinates to the display surface for the
copy.  With this patch I can drag a window with no screen corruption.

Signed-off-by: Brian Kress <kressb@moose.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6622 c046a42c-6fe2-441c-8c8c-71466251a162