hw/display/tcx: Allow 64-bit accesses to framebuffer stippler and blitter

hw/display/tcx: Allow 64-bit accesses to framebuffer stippler and blitter

The S24/TCX datasheet is listed as "Unable to locate" on [1].

However the NetBSD revision 1.32 of the driver introduced
64-bit accesses to the stippler and blitter [2]. It is safe
to assume these memory regions are 64-bit accessible.
QEMU implementation is 32-bit, so fill the 'impl' fields.

Michael Lorenz (author of the NetBSD code [2]) provided us with more
information in [3]:

> IIRC the real hardware *requires* 64bit accesses for stipple and
> blitter operations to work. For stipples you write a 64bit word into
> STIP space, the address defines where in the framebuffer you want to
> draw, the data contain a 32bit bitmask, foreground colour and a ROP.
> BLIT space works similarly, the 64bit word contains an offset were to
> read pixels from, and how many you want to copy.
>
> One more thing since there seems to be some confusion - 64bit accesses
> on the framebuffer are fine as well. TCX/S24 is *not* an SBus device,
> even though its node says it is.
> S24 is a card that plugs into a special slot on the SS5 mainboard,
> which is shared with an SBus slot and looks a lot like a horizontal
> UPA slot. Both S24 and TCX are accessed through the Micro/TurboSPARC's
> AFX bus which is 64bit wide and intended for graphics.
> Early FFB docs even mentioned connecting to both AFX and UPA,
> no idea if that was ever realized in hardware though.

[1] http://web.archive.org/web/20111209011516/http://wikis.sun.com/display/FOSSdocs/Home
[2] http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/dev/sbus/tcx.c.diff?r1=1.31&r2=1.32
[3] https://www.mail-archive.com/qemu-devel@nongnu.org/msg734928.html

Cc: qemu-stable@nongnu.org
Reported-by: Andreas Gustafsson <gson@gson.org>
Buglink: https://bugs.launchpad.net/bugs/1892540
Fixes: 55d7bfe2293 ("tcx: Implement hardware acceleration")
Tested-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Andreas Gustafsson <gson@gson.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201024205100.3623006-1-f4bug@amsat.org>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>