defconfig: msm8974: Enable Chipidea USB2 gadget controller driver

8974 has two USB cores: Synopsys USB3 and Chipidea USB2.
Currently DWC3 gadget is enabled to use DWC3 as primary OTG port.
However some 8974 platforms might want to use USB3 in host only
mode and USB2 in OTG mode. Hence, enable both DWC3 and Chipidea
USB2 drivers to support all the configurations based on DT
parameters passed.

Change-Id: Ib6d351432a8b47d86a76d57934abc149d1dd6a35
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>