phy: hix5hd2-sata: Check return value of platform_get_resource

This prevent NULL pointer dereference if res is NULL.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>