UPSTREAM: coresight tmc etr: Make memory check consistent in the same function

While operating from sysFS the TMC-ETR driver needs to make sure it has
memory to work with but doesn't allocate memory uselessly either.  Since
the main memory handle for this driver is drvdata::vaddr, use it throughout
function tmc_enable_etr_sink_sysfs() so that things are consistent.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(Upstream commit 3606a1dcb46eee173203702b6b19cd898afa5d15).

Bug: 140266694
Change-Id: I2a0435ae0eeb8b38858e73d65db1a24149b4ea95
Signed-off-by: Yabin Cui <yabinc@google.com>