input: it7258_ts_i2c: add debugfs support for suspend/resume

Add debugfs support for suspend and resume test for ITE
tech touchscreen driver.

This is propagation gerrit for 8909w bring up.

Change-Id: I5a3d55c7c8e4b8f594fd7924c61ac1e5b5ad1965
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>