spl: Fix guardian macros in spl.h

Fix the macros guarding the spl.h header for various platforms. Due to
a typo and a propagation of it, the macros went out-of-sync with their
ifdef check, so fix this.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Tom Rini <trini@ti.com>
diff --git a/arch/arm/include/asm/arch-am33xx/spl.h b/arch/arm/include/asm/arch-am33xx/spl.h
index 2df4114..8543f43 100644
--- a/arch/arm/include/asm/arch-am33xx/spl.h
+++ b/arch/arm/include/asm/arch-am33xx/spl.h
@@ -5,7 +5,7 @@
  * SPDX-License-Identifier:	GPL-2.0+
  */
 #ifndef	_ASM_ARCH_SPL_H_
-#define	_ASM_SPL_H_
+#define	_ASM_ARCH_SPL_H_
 
 #if defined(CONFIG_TI816X)
 #define BOOT_DEVICE_XIP		2