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 <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>
diff --git a/subsys/logging/Kconfig.processing b/subsys/logging/Kconfig.processing
index 36d8cec..c1af0f2 100644
--- a/subsys/logging/Kconfig.processing
+++ b/subsys/logging/Kconfig.processing
@@ -78,6 +78,7 @@
 	int "Stack size for the internal log processing thread"
 	default 4096 if (X86 && X86_64)
 	default 4096 if ARM64
+	default 4096 if (ARC && 64BIT)
 	default 4096 if SPARC
 	default 2048 if COVERAGE_GCOV
 	default 2048 if (RISCV && 64BIT)