arm: Set up global data before board_init_f()

At present arm defines CONFIG_SYS_GENERIC_GLOBAL_DATA, meaning that
the global_data pointer is set up in board_init_f(). However it is
actually set up before this, it just isn't zeroed.

If we zero the global data before calling board_init_f() then we
don't need to define CONFIG_SYS_GENERIC_GLOBAL_DATA.

Make this change (on arm32 only) to simplify the init process. I
don't have the ability to test aarch64 yet.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Tom Rini <trini@ti.com>

arch/arm/include/asm/config.h

@@ -7,7 +7,9 @@
 #ifndef _ASM_CONFIG_H_
 #define _ASM_CONFIG_H_
 
+#ifdef __aarch64__
 #define CONFIG_SYS_GENERIC_GLOBAL_DATA
+#endif
 
 #define CONFIG_LMB
 #define CONFIG_SYS_BOOT_RAMDISK_HIGH

arch/arm/lib/crt0.S

@@ -67,10 +67,19 @@ ENTRY(_main)
 	ldr	sp, =(CONFIG_SYS_INIT_SP_ADDR)
 #endif
 	bic	sp, sp, #7	/* 8-byte alignment for ABI compliance */
+	mov	r2, sp
 	sub	sp, sp, #GD_SIZE	/* allocate one GD above SP */
 	bic	sp, sp, #7	/* 8-byte alignment for ABI compliance */
 	mov	r9, sp		/* GD is above SP */
+	mov	r1, sp
 	mov	r0, #0
+clr_gd:
+	cmp	r1, r2			/* while not at end of GD */
+	strlo	r0, [r1]		/* clear 32-bit GD word */
+	addlo	r1, r1, #4		/* move to next */
+	blo	clr_gd
+
+	/* mov r0, #0 not needed due to above code */
 	bl	board_init_f
 
 #if ! defined(CONFIG_SPL_BUILD)