coresight: use no log version of readl while dumping etf

During kernel panic, coresight_abort is first called to stop
tracing to the default ETF (circular buffer mode) sink. This is
followed by stopping RTB as part of the panic handler.

Use no log version of readl while dumping ETF in circular buffer
mode to avoid polluting RTB logs with readls responsible for
dumping ETF during kernel panic.

Change-Id: I282516be458c8b38af20cb372803cdff9eb9e8f0
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>