coresight: funnel: Support static funnel

Since CoreSight hardware topology can use a 'hidden' funnel in the
trace data path, this kind funnel doesn't have register for accessing
and is used by default from hardware design perspective.  Below is an
example for related hardware topology:

  +------+  +------+
  | cpu0 |->| ETM  |-\
  +------+  +------+  \-> +--------+  +-----+
   ......                 | Funnel |->| ETF |-\    Hidden funnel
  +------+  +------+  /-> +--------+  +-----+  \        |
  | cpu3 |->| ETM  |-/                          \       V
  +------+  +------+                             \-> +--------+
                                                     | Funnel |-> ...
  +------+  +------+                             /-> +--------+
  | cpu4 |->| ETM  |-\                          /
  +------+  +------+  \-> +--------+  +-----+  /
   ......                 | Funnel |->| ETF |-/
  +------+  +------+  /-> +--------+  +-----+
  | cpu7 |->| ETM  |-/
  +------+  +------+

The CoreSight funnel driver only supports dynamic funnel with
registration register resource, thus it cannot support for the static
funnel case and it's impossible to create trace data path for this case.

This patch is to extend CoreSight funnel driver to support both for
static funnel and dynamic funnel.  For the dynamic funnel it reuses the
code existed in the driver, for static funnel the driver will support
device probe if without providing register resource and the driver skips
registers accessing when detect the register base is NULL.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Wanglai Shi <shiwanglai@hisilicon.com>
Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>