ARC: 64BIT: increase LOG_PROCESS_THREAD stack size
ARC: 64BIT: increase LOG_PROCESS_THREAD stack size

Increase LOG_PROCESS_THREAD_STACK_SIZE for ARCv3 64 bit to
fix failing test
tests/subsys/logging/log_core_additional/logging.add.async
due to stack overflow.

Signed-off-by: Eugeniy Paltsev <ec089b543c2604b626d7ce60c03e4d074ed102c7@synopsys.com>
Signed-off-by: Evgeniy Paltsev <7de4ab8b01334d64e4e84734c688a8a936513edc@gmail.com>

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