Enable USB gadget for RPI4

Enable USB gadget for RPI4

You can use this usb hal with both RPI3 and RPI4.
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RPI3 does not have /sys/kernel/config and usb initialization faiied.
So, usb is not enabled in RPI3.
Therefore, a single usb hal can be used in both RPI3 and RPI4.

Deviced internal design for extcon providing incomplete functionality
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Excon does not work perfectly in RPI4
So I asked the kernel team to fix the extcon value to 1.
If extcon is always 1, deviecd will not recognize when usb is disconnected, but it will work normally.

Conclusion: For targets where extcon does not work perfectly, deviced do not support usb connect/disconnect.

Change-Id: Iea3ae481b3120432197a849956fc5332748957ad
Signed-off-by: INSUN PYO <insun.pyo@samsung.com>