spl: Remove bogus GD_FLG_SPL_INIT check

Remove the check for GD_FLG_SPL_INIT in spl_relocate_stack_gd().
The check will always fail. This is because spl_relocate_stack_gd()
is called from ARM's crt0.S and it is called before board_init_r().
The board_init_r() calls spl_init(), which sets the GD_FLG_SPL_INIT
flag.

Note that reserving the malloc area in RAM is not a problem even
if the GD_FLG_SPL_INIT flag is not set.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Pavel Machek <pavel@denx.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Stephen Warren <swarren@nvidia.com>