arm: mach-k3: k3-ddr.h: Include spl.h

Include spl.h to avoid definition errors in custom builds.

Fixes: commit bc07851897bd ("board: ti: Pull redundant DDR functions to a common location and Fixup DDR size when ECC is enabled")
Signed-off-by: Neha Malcom Francis <n-francis@ti.com>
diff --git a/arch/arm/mach-k3/include/mach/k3-ddr.h b/arch/arm/mach-k3/include/mach/k3-ddr.h
index 95496e1..39e6725 100644
--- a/arch/arm/mach-k3/include/mach/k3-ddr.h
+++ b/arch/arm/mach-k3/include/mach/k3-ddr.h
@@ -6,6 +6,8 @@
 #ifndef _K3_DDR_H_
 #define _K3_DDR_H_
 
+#include <spl.h>
+
 int dram_init(void);
 int dram_init_banksize(void);