[why]
if dynamic allocation fails during gpio_open, it will cause crash due to
page fault.

[how]
handle allocation when gpio object gets created and prevent from calling
gpio_open if allocation failed
Signed-off-by: Su Sung Chung <Su.Chung@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>