usb: gadget: f_gsi: Add handling of SET_CONTROL_LINE_STATE control request

CDC control request SET_CONTROL_LINE_STATE  was not handled in
gsi_setup(). This is needed for RmNet functionality.
This led to below warnings seen on the console any time the RmNet
function is activated.
	gsi_setup: inval ctrl req21.22 v0000 i0004 l0
	gsi_setup: inval ctrl req21.22 v0001 i0004 l0
So add the support to handle SET_CONTROL_LINE_STATE request.

Change-Id: I16e9fd07a69fe6606d3a5f23a20523ad5509d24a
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>