coresight: tpdm: fix invalid MMIO access issue

coresight: tpdm: fix invalid MMIO access issue

Create the csdev_access struct only when a valid MMIO resource is
available. In tpdm_probe(), base is uninitialized for static TPDM
instances that lack an MMIO resource, causing csdev_access to be
created with a garbage address.

So far there has no register access for static instance, but this
change helps mitigate potential risks in the future.

Fixes: 14ae052f7947 ("coresight: tpdm: add static tpdm support")
Reviewed-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20260407-fix-potential-issue-in-tpdm-v2-1-1d0e0d3cb793@oss.qualcomm.com