test(realm): add test for RSI_PLANE_REG_READ/WRITE command

test for RSI_PLANE_REG_READ/WRITE command

Signed-off-by: Shruti Gupta <shruti.gupta@arm.com>
Change-Id: I92e0aeef48c9b2abe26e5d3b2ea62669a22d4f8b
diff --git a/realm/include/realm_rsi.h b/realm/include/realm_rsi.h
index e72a769..06f857f 100644
--- a/realm/include/realm_rsi.h
+++ b/realm/include/realm_rsi.h
@@ -270,6 +270,12 @@
  */
 #define RSI_PLANE_REG_READ	SMC_RSI_FID(0x1EU)
 
+u_register_t rsi_plane_reg_read(u_register_t plane_index, u_register_t register_encoding,
+		u_register_t *value);
+
+u_register_t rsi_plane_reg_write(u_register_t plane_index, u_register_t register_encoding,
+		u_register_t value);
+
 /*
  * arg1 == plane index
  * arg2 == register encoding