coresight: trbe: Allocate platform data per device

Coresight TRBE driver shares a single platform data (which is empty btw).
However, with the commit 4e8fe7e5
("coresight: Store pointers to connections rather than an array of them")
the coresight core would free up the pdata, resulting in multiple attempts
to free the same pdata for TRBE instances. Fix this by allocating a pdata per
coresight_device.

Fixes: 4e8fe7e5

 ("coresight: Store pointers to connections rather than an array of them")
Link: https://lore.kernel.org/r/20230814093813.19152-3-hejunhao3@huawei.com
Reported-by: Junhao He <hejunhao3@huawei.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: James Clark <james.clark@arm.com>
Tested-by: Junhao He <hejunhao3@huawei.com>
Link: https://lore.kernel.org/r/20230816141008.535450-2-suzuki.poulose@arm.com
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>