brcmfmac: Fix memory leak in brcmf_usbdev_qinit

In the implementation of brcmf_usbdev_qinit() the allocated memory for
reqs is leaking if usb_alloc_urb() fails. Release reqs in the error
handling path.

Fixes: 71bb244b ("brcm80211: fmac: add USB support for bcm43235/6/8 chipsets")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>