ENGR00173962 Added HDMI enable function

ENGR00173962 Added HDMI enable function

Whenever IPU clock change or gating, the HDMI PHY should reset or config again,
otherwise the HDMI PHY will not work.
It is the root cause for Ubuntu can't show GUI to HDMI device when bootup
and GPU application tutorial4_es20 no output to HDMI device.
Added enable function in mxcfb_set_par() to fix aboved two issue.

Added HDMI initialization check, only one HDMI instanse supported.

Signed-off-by: Sandor Yu <R01008@freescale.com>