usbip: add USBIP_URB_* URB transfer flags

USBIP driver packs URB transfer flags in network packets that are
exchanged between Server (usbip_host) and Client (vhci_hcd).

URB_* flags are internal to kernel and could change. Where as USBIP
URB flags exchanged in network packets are USBIP user API must not
change.

Add USBIP_URB* flags to make this an explicit API and change the
client and server to map them. Details as follows:

Client tx path (USBIP_CMD_SUBMIT):
- Maps URB_* to USBIP_URB_* when it sends USBIP_CMD_SUBMIT packet.

Server rx path (USBIP_CMD_SUBMIT):
- Maps USBIP_URB_* to URB_* when it receives USBIP_CMD_SUBMIT packet.

Flags aren't included in USBIP_CMD_UNLINK and USBIP_RET_SUBMIT packets
and no special handling is needed for them in the following cases:

- Server rx path (USBIP_CMD_UNLINK)
- Client rx path & Server tx path (USBIP_RET_SUBMIT)

Update protocol documentation to reflect the change.

Suggested-by: Hongren Zenithal Zheng <i@zenithal.me>
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20220824002456.94605-1-skhan@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

License cleanup: add SPDX license identifier to uapi header files with no license

Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine the correct license.

By default are files without license information under the default
license of the kernel, which is GPLV2. Marking them GPLV2 would exclude
them from being included in non GPLV2 code, which is obviously not
intended. The user space API headers fall under the syscall exception
which is in the kernels COPYING file:

NOTE! This copyright does *not* cover user programs that use kernel
services by normal system calls - this is merely considered normal use
of the kernel, and does *not* fall under the heading of "derived work".

otherwise syscall usage would not be possible.

Update the files which contain no license information with an SPDX
license identifier. The chosen identifier is 'GPL-2.0 WITH
Linux-syscall-note' which is the officially assigned identifier for the
Linux syscall exception. SPDX license identifiers are a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne. See the previous patch in this series for the
methodology of how this patch was researched.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

usbip: move usbip kernel code out of staging

At this point, USB/IP kernel code is fully functional
and can be moved out of staging.

Signed-off-by: Valentina Manea <valentina.manea.m@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>