MLK-12948 ARM: dts: imx7d-sdb: change the hardware reset gpio for mipi dsi

MLK-12948 ARM: dts: imx7d-sdb: change the hardware reset gpio for mipi dsi

Change the hardware reset gpio to 'GPIO6_IO15' for mipi dsi to
allow fec2 and mipi dsi can run at the same time. This needs
some hardware rework as follows:
"
    1. Replace R631 with 100K resistor;
    2. Remove D14, D24;
    3. Solder the Cathode of the diode to R471,
       you can use BAT54HT1(ONSEMI) or NSR0320MW2T1G(ONSEMI);
    4. Solder the wire to the Anode end of the diode;
    5. Scrape the solder mask(Green oil)  of the MIPI Reset via,
       then solder the end of the wire to the via.
"

Signed-off-by: Fancy Fang <chen.fang@nxp.com>
Signed-off-by: Arulpandiyan Vadivel <arulpandiyan_vadivel@mentor.com>
Signed-off-by: Srikanth Krishnakar <Srikanth_Krishnakar@mentor.com>