staging: Use pr_warn instead of pr_warning

As said in commit f2c2cbcc ("powerpc: Use pr_warn instead of
pr_warning"), removing pr_warning so all logging messages use a
consistent <prefix>_warn style. Let's do it.

Cc: Karsten Keil <isdn@linux-pingi.de>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Link: https://lore.kernel.org/r/20190920062544.180997-22-wangkefeng.wang@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>