dt-bindings: mhi: remove tsync fields as no longer needed in device tree

Updated the device tree documentation to remove timesync fields
since core driver no longer requires it.

CRs-Fixed: 2332909
Change-Id: I533731efb2668e4b933dea7d07e6d28a86a76eaa
Acked-by: Bhaumik Vasav Bhatt <bbhatt@qti.qualcomm.com>
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>