usb: gadget: f_hid: fixed NULL pointer dereference

stable inclusion
from stable-5.10.58
commit 825ac3f0bc3516a3a93f48c573f7cb8f4f0d86fe
bugzilla: 176984 https://gitee.com/openeuler/kernel/issues/I4E2P4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=825ac3f0bc3516a3a93f48c573f7cb8f4f0d86fe

--------------------------------

commit 2867652e upstream.

Disconnecting and reconnecting the USB cable can lead to crashes
and a variety of kernel log spam.

The problem was found and reproduced on the Raspberry Pi [1]
and the original fix was created in Raspberry's own fork [2].

Link: https://github.com/raspberrypi/linux/issues/3870 [1]
Link: https://github.com/raspberrypi/linux/commit/a6e47d5f4efbd2ea6a0b6565cd2f9b7bb217ded5

 [2]
Signed-off-by: Maxim Devaev <mdevaev@gmail.com>
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210723155928.210019-1-mdevaev@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>