improve error logging

• hw-lock: log return address when lock is busy
• pmic: print strerror(errno)

epicardium/modules/hw-lock.c

@@ -27,7 +27,12 @@ int hwlock_acquire(enum hwlock_periph p, TickType_t wait)
 	}
 
 	if (xSemaphoreTake(hwlock_mutex[p], wait) != pdTRUE) {
-		LOG_WARN("hwlock", "Lock %u is busy.", p);
+		LOG_WARN(
+			"hwlock",
+			"Lock %u is busy. [pc %p]",
+			p,
+			__builtin_return_address(0)
+		);
 		return -EBUSY;
 	}