coresight: stm: Read debug fuse status for stm from nvmem

Use the nvmem APIs to get the debug fuse status to set debug status
for stm when stm-debug-status register is not configured.

Change-Id: Ib2719ce5e5a2b59ebb50a507331a5ecb91c2ea9d
Signed-off-by: Mao Jinlong <jinlmao@codeaurora.org>