hw/mips/gt64xxx: Remove dynamic field width from trace events

hw/mips/gt64xxx: Remove dynamic field width from trace events

Since not all trace backends support dynamic field width in
format (dtrace via stap does not), replace by a static field
width instead.

We previously passed to the trace API 'width << 1' as the number
of hex characters to display (the dynamic field width). We don't
need this anymore. Instead, display the size of bytes accessed.

Fixes: ab6bff424f ("gt64xxx_pci: Convert debug printf to trace events")
Reported-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>