In OS descriptors handling, if ctrl->bRequestType is
USB_RECIP_DEVICE and w_index != 0x4 or (w_value >> 8)
is true, it will not assign a valid value to req->length,
but use the default value(-EOPNOTSUPP), and queue an
OS desc request with the invalid req->length. It always
happens on the platforms which use os_desc (for example:
rk3366, rk3399), and cause kernel panic as follows
(use dwc3 driver):

Unable to handle kernel paging request at virtual address ffffffc0f7e00000
Internal error: Oops: 96000146 [#1] PREEMPT SMP
PC is at __dma_clean_range+0x18/0x30
LR is at __swiotlb_map_page+0x50/0x64
Call trace:
[<ffffffc0000930f8>] __dma_clean_range+0x18/0x30
[<ffffffc00062214c>] usb_gadget_map_request+0x134/0x1b0
[<ffffffc0005c289c>] __dwc3_ep0_do_control_data+0x110/0x14c
[<ffffffc0005c2d38>] __dwc3_gadget_ep0_queue+0x198/0x1b8
[<ffffffc0005c2e18>] dwc3_gadget_ep0_queue+0xc0/0xe8
[<ffffffc00061cfec>] composite_ep0_queue.constprop.14+0x34/0x98
[<ffffffc00061dfb0>] composite_setup+0xf60/0x100c
[<ffffffc0006204dc>] android_setup+0xd8/0x138
[<ffffffc0005c29a4>] dwc3_ep0_delegate_req+0x34/0x50
[<ffffffc0005c3534>] dwc3_ep0_interrupt+0x5dc/0xb58
[<ffffffc0005c0c3c>] dwc3_thread_interrupt+0x15c/0xa24

With this patch, the gadget driver will not queue
a request and return immediately if req->length is
invalid. And the usb controller driver can handle
the unsupport request correctly.

Signed-off-by: William Wu <william.wu@rock-chips.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>