firmware: zynqmp: Enable IPI code calling also in EL3

U-Boot proper can still run in EL3 without using firmware interface wired
via ATF. For supporting this use case there is a need to check EL level
where U-Boot runs and based on that choose the way how to talk to firmware.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/drivers/firmware/firmware-zynqmp.c b/drivers/firmware/firmware-zynqmp.c
index 2a2aa2f..c376425 100644
--- a/drivers/firmware/firmware-zynqmp.c
+++ b/drivers/firmware/firmware-zynqmp.c
@@ -51,7 +51,7 @@
 
 static int send_req(const u32 *req, size_t req_len, u32 *res, size_t res_maxlen)
 {
-	if (IS_ENABLED(CONFIG_SPL_BUILD))
+	if (IS_ENABLED(CONFIG_SPL_BUILD) || current_el() == 3)
 		return ipi_req(req, req_len, res, res_maxlen);
 
 	return xilinx_pm_request(req[0], 0, 0, 0, 0, res);