mx6sabreauto: set SYS_MALLOC_F for video

mx6sabreauto: set SYS_MALLOC_F for video

Sabre Auto boards currently hang with:
```
U-Boot 2019.07-rc3-00057-gc41940c406 (Jun 03 2019 - 14:42:41 +0200)

CPU:   Freescale i.MX6QP rev1.0 996 MHz (running at 792 MHz)
CPU:   Automotive temperature grade (-40C to 125C)Reset cause: WDOG
Model: Freescale i.MX6 Quad Plus SABRE Automotive Board
Board: MX6Q-Sabreauto revA
I2C:   ready
DRAM:  2 GiB
Video device 'ipu@2400000' cannot allocate frame buffer memory -ensure the device is set up before relocation
Error binding driver 'ipuv3_video': -28
Video device 'ipu@2800000' cannot allocate frame buffer memory -ensure the device is set up before relocation
Error binding driver 'ipuv3_video': -28
Some drivers failed to bind
Error binding driver 'generic_simple_bus': -28
Some drivers failed to bind
initcall sequence 8ffe00b8 failed at call 1780e93b (err=-28)
```

Set SYS_MALLOC_F_LEN to reserve_video to work.

This is similar to the change Peng Fan did for mx6sabresd (9002e735e717)

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Reviewed-by: Peng Fan <peng.fan@nxp.com>