drivers: qcom: rpmh-rsc: do not read back the register write on trigger

When triggering a TCS to send its contents, reading back the trigger
value may return an incorrect value. That is because, writing the
trigger may raise an interrupt which could be handled immediately and
the trigger value could be reset in the interrupt handler.

A write_tcs_reg_sync() would read back the value that is written and try
to match it to the value written to ensure that the value is written,
but if that value is different, we are stuck in loop forever.

Change-Id: I54866b9b9d85fa79c8df84aecd502764b9f9158a
Signed-off-by: Lina Iyer <ilina@codeaurora.org>