pinctrl: Fix early return in sky1_pinconf_group_dbg_show

[USAVault]

In sky1_pinconf_get(): add a guard for pin_regs[pin_id] == -1 and return -EINVAL, without it, unconfigured pins lead to an invalid readl(base + 0xFFFFFFFF) access

In sky1_pinconf_group_dbg_show(): the unconditional return inside the loop was intended to be conditional. I believe it should have been if (ret) return, as the extra indent level suggests the author’s intent, so the logic is updated to match the mainline imx_pinconf_group_dbg_show pattern