usb: gadget: gsi: Add a debugfs entry to simulate remote wakeup

Add a debugfs entry to simulate IPA callback for remote wakeup
on USB side. On executing the below command a timer will be
started and remote wakeup will be done for every specified
time interval.

- To enable timer execute the below command:
echo 1 > /sys/kernel/debug/usb_gsi/remote_wakeup_enable

- To disable timer execute the below command:
echo 0 > /sys/kernel/debug/usb_gsi/remote_wakeup_enable

- To update timer value, execute the below command (default 500 ms):
echo 5000 > /sys/kernel/debug/usb_gsi/remote_wakeup_interval

Change-Id: I0799123710e064311321593b893e06940a54aa14
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>
Signed-off-by: Mayank Rana <mrana@codeaurora.org>
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>