vgacon: use slab allocator instead of the bootmem allocator

Slab is initialized before the console subsystem so use the slab allocator in
vgacon_scrollback_startup().
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>

drivers/video/console/vgacon.c

@@ -180,7 +180,7 @@ static inline void vga_set_mem_top(struct vc_data *c)
 }
 
 #ifdef CONFIG_VGACON_SOFT_SCROLLBACK
-#include <linux/bootmem.h>
+#include <linux/slab.h>
 /* software scrollback */
 static void *vgacon_scrollback;
 static int vgacon_scrollback_tail;
@@ -210,8 +210,7 @@ static void vgacon_scrollback_init(int pitch)
  */
 static void __init_refok vgacon_scrollback_startup(void)
 {
-	vgacon_scrollback = alloc_bootmem(CONFIG_VGACON_SOFT_SCROLLBACK_SIZE
-					  * 1024);
+	vgacon_scrollback = kcalloc(CONFIG_VGACON_SOFT_SCROLLBACK_SIZE, 1024, GFP_NOWAIT);
 	vgacon_scrollback_init(vga_video_num_columns * 2);
 }