coresight: tmc: keep track of memory width

coresight: tmc: keep track of memory width

Accessing the HW configuration register each time the memory
width is needed simply doesn't make sense.  It is much more
efficient to read the value once and keep a reference for
later use.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 4f1ff3de925d741b0b77c59bc1387cb940ad7c73)