input: touchscreen: Add debugfs support for suspend/resume.

Add debugfs entry for suspend/resume that allow suspending/
resuming of Goodix CTP driver from userspace.
Also change the return type of goodix_ts_resume and
goodix_ts_suspend functions and set the status of
gtp_is_suspended in the last of above functions.

CRs-fixed: 554796
Change-Id: Ic2b1b2562b63ccecdf15bdc64ad7e45996d196d3
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>