arc: get rid of CONFIG_SYS_GENERIC_GLOBAL_DATA

As discussed on mailing list we're drifting away from
CONFIG_SYS_GENERIC_GLOBAL_DATA in favour to use of board_init_f_mem()
for global data.

So do this for ARC architecture.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
diff --git a/arch/arc/lib/start.S b/arch/arc/lib/start.S
index 82045ae..48ee86e 100644
--- a/arch/arc/lib/start.S
+++ b/arch/arc/lib/start.S
@@ -22,6 +22,14 @@
 	bl	dcache_disable
 	bl	icache_disable
 
+	/* Allocate and zero GD, update SP */
+	mov	%r0, %sp
+	bl	board_init_f_mem
+
+	/* Update stack- and frame-pointers */
+	mov	%sp, %r0
+	mov	%fp, %sp
+
 	/* Zero the one and only argument of "board_init_f" */
 	mov_s	%r0, 0
 	j	board_init_f