mx6sabresd: Reset counter to prevent error message

mx6sabresd: Reset counter to prevent error message

If a HDMI cable is not connected, the following message is seen on boot:

CPU:   Freescale i.MX6Q rev1.1 at 792 MHz
Reset cause: POR
Board: MX6-SabreSD
DRAM:  1 GiB
MMC:   FSL_SDHC: 0, FSL_SDHC: 1, FSL_SDHC: 2
No panel detected: default to HDMI
unsupported panel HDMI

Reset the 'i' variable to fix the 'unsupported panel' message.

This follows the same idea of commit 47ac53d7ae (imx: nitrogen6x/mx6qsabrelite:
Fix bug in board_video_skip).

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>