media:uvc: supports dynamic setting of urb configuration

Frames are corrupted for higher resolution with default URB queue
size and frame size. This patch creates a sysfs node to support
dynamic setting of number of packers per urb  and maximum packet
size for higher resolution frames.
$ find . -name urb_config.
$ echo qsize:fsize > urb_config.

Change-Id: I70aaad824049acdc21a8a52242066a6437b96833
Signed-off-by: Arjun Singh <quic_arsingh@quicinc.com>