docs: Fix typo (wphx => whpx)

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1529


Signed-off-by: Stefan Weil <sw@weilnetz.de>
Message-Id: <20230409201007.1157671-1-sw@weilnetz.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>