net/fm: Add support for 64-bit platforms

The FMan IM driver is developed for 32-bit platfroms and isn't
friendly to 64-bit platforms, so do the minimal refactor:

1. Refine the MURAM management and access.
2. Correct the initialization and operations for QDs and BDs.

Signed-off-by: Hou Zhiqiang <B48286@freescale.com>
Signed-off-by: Gong Qianyu <Qianyu.Gong@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>