Add mode selection to iMX6 IPU driver

• Configure ipu1_di0 tob e sourced from the VIDEO_PLL(PLL5) and hardcode frequency to (455000000/3)Mhz. This value, further divided, can yield frequencies close enough to support 1080p, 720p, 1024x768, and 640x480 modes. This is not ideal but it's an improvement comparing to the only hardcoded 1024x768 mode.

• Fix memory leaks if attach method failed
• Print EDID when -v passed to the kernel