arm: Switch aarch64 to using generic global_data setup

There is quite a bit of assembler code that can be removed if we use the
generic global_data setup. Less arch-specific code makes it easier to add
new features and maintain the start-up code.

Drop the unneeded code and adjust the hooks in board_f.c to cope.

Tested on LS2085ARDB and LS2085AQDS (armv8 SoC).
Tested-by: NYork Sun <yorksun@freescale.com>
Signed-off-by: NSimon Glass <sjg@chromium.org>

arch/arm/lib/crt0_64.S

@@ -73,20 +73,11 @@ ENTRY(_main)
 	ldr	x0, =(CONFIG_SPL_STACK)
 #else
 	ldr	x0, =(CONFIG_SYS_INIT_SP_ADDR)
-#endif
-	sub	x18, x0, #GD_SIZE	/* allocate one GD above SP */
-	bic	x18, x18, #0x7		/* 8-byte alignment for GD */
-zero_gd:
-	sub	x0, x0, #0x8
-	str	xzr, [x0]
-	cmp	x0, x18
-	b.gt	zero_gd
-#if defined(CONFIG_SYS_MALLOC_F_LEN)
-	ldr	x0, =CONFIG_SYS_MALLOC_F_LEN
-	sub	x0, x18, x0
-	str	x0, [x18, #GD_MALLOC_BASE]
 #endif
 	bic	sp, x0, #0xf	/* 16-byte alignment for ABI compliance */
+	bl	board_init_f_mem
+	mov	sp, x0
+
 	mov	x0, #0
 	bl	board_init_f