uboot-imx

MAINTAINERS: Update no longer valid maintainers' status

The following maintainers' email addresses are no longer valid.

vipin.kumar@st.com
martin.krause@tq-systems.de
kim.phillips@freescale.com
fgretief@spaceteq.co.za

Update status of the components they used to maintain to be:
S: Orphaned (Since 2016-02)

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>