86xx: remove the redundant r2 global data pointer save

The commit 67256678 add
the another global data pointer save, but in fact the
global data pointer will be initialized in the board_init_r,
so remove it such as the 85xx/83xx family.

Signed-off-by: Dave Liu <daveliu@freescale.com>
Acked-by: Kumar Gala <kumar.gala@freescale.com>