powerpc/ps3: Move static keyword to the front of declaration

Move the static keyword to the front of declaration of 'vuart_bus_priv',
and resolve the following compiler warning that can be seen when
building with warnings enabled (W=1):

drivers/ps3/ps3-vuart.c:867:1: warning: ‘static’ is not at beginning of declaration [-Wold-style-declaration]
 } static vuart_bus_priv;
 ^

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1588154448-56759-1-git-send-email-wangxiongfeng2@huawei.com