ipc: icbmsg: Fix issue in bsim integration

Add call to Z_SPIN_DELAY() to avoid issue in bsim where
time does not progress in loop causing other threads to
starve.

Upstream PR: zephyrproject-rtos/zephyr#80043

Author: jostn

subsys/ipc/ipc_service/backends/ipc_icbmsg.c

@@ -1061,6 +1061,7 @@ static int send(const struct device *instance, void *token, const void *msg, siz
 	alloc_size = len;
 	r = alloc_tx_buffer(dev_data, &alloc_size, &buffer, K_NO_WAIT);
 	if (r < 0) {
+		Z_SPIN_DELAY(1);
 		return r;
 	}