tmc-etr: Disable all sources/sinks to avoid Flash bit hang issue

ManuFlash bit will hang there for some abnormal cases. Disable all
sources and sinks before set the manuFlash bit during mode_switch
to fix this issue.

Change-Id: I74f695e0acff9fc9a63e1e2204746a7a40176d15
Signed-off-by: Mao Jinlong <jinlmao@codeaurora.org>