[fbcon] Update the console width and height after changing mode

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/fbcon.c

 #include <ipxe/image.h>
 #include <ipxe/pixbuf.h>
 #include <ipxe/umalloc.h>
+#include <ipxe/console.h>
 #include <ipxe/fbcon.h>
 
 /**
 	/* Clear screen */
 	fbcon_clear ( fbcon, 0 );
 
+	/* Update console width and height */
+	console_set_size ( fbcon->character.width, fbcon->character.height );
+
 	return 0;
 
 	ufree ( fbcon->picture.start );