usb: musb: dsps: Fix the probe error path

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

usb: musb: dsps: Fix the probe error path

Commit 7c75bde329d7 ("usb: musb: musb_dsps: request_irq() after

initializing musb") has inverted the calls to

dsps_setup_optional_vbus_irq() and dsps_create_musb_pdev() without

updating correctly the error path. dsps_create_musb_pdev() allocates and

registers a new platform device which must be unregistered and freed

with platform_device_unregister(), and this is missing upon

dsps_setup_optional_vbus_irq() error.

While on the master branch it seems not to trigger any issue, I observed

a kernel crash because of a NULL pointer dereference with a v5.10.70

stable kernel where the patch mentioned above was backported. With this

kernel version, -EPROBE_DEFER is returned the first time

dsps_setup_optional_vbus_irq() is called which triggers the probe to

error out without unregistering the platform device. Unfortunately, on

the Beagle Bone Black Wireless, the platform device still living in the

system is being used by the USB Ethernet gadget driver, which during the

boot phase triggers the crash.

My limited knowledge of the musb world prevents me to revert this commit

which was sent to silence a robot warning which, as far as I understand,

does not make sense. The goal of this patch was to prevent an IRQ to

fire before the platform device being registered. I think this cannot

ever happen due to the fact that enabling the interrupts is done by the

->enable() callback of the platform musb device, and this platform

device must be already registered in order for the core or any other

user to use this callback.

Hence, I decided to fix the error path, which might prevent future

errors on mainline kernels while also fixing older ones.