CVE-2024-46691: usb: typec: ucsi: Move unregister out of atomic section

In the Linux kernel, the following vulnerability has been resolved:

usb: typec: ucsi: Move unregister out of atomic section

Commit '9329933699b3 ("soc: qcom: pmicglink: Make client-lock non-sleeping")' moved the pmicglink client list under a spinlock, as it is accessed by the rpmsg/glink callback, which in turn is invoked from IRQ context.

This means that ucsiunregister() is now called from atomic context, which isn't feasible as it's expecting a sleepable context. An effort is under way to get GLINK to invoke its callbacks in a sleepable context, but until then lets schedule the unregistration.

A side effect of this is that ucsiunregister() can now happen after the remote processor, and thereby the communication link with it, is gone. pmicglinksend() is amended with a check to avoid the resulting NULL pointer dereference. This does however result in the user being informed about this error by the following entry in the kernel log:

ucsiglink.pmicglinkucsi pmicglink.ucsi.0: failed to send UCSI write request: -5