libdma: adding memset support

extending the DMA library to support memset transfers for the
Intel IOAT DMA device.

libdma: refactoring of driver client as a "virtual" dma device

The DMA clients are now acting as a "normal" dma device where the
requests are forwared to the DMA driver service domain instead of
serving locally. The client initializes a DMA device by service name,
iref or supported memory range.

Extended the DMA manager to serve iref based queries.

Several generalizations of some device/channel functions to handle the
requests and forward them to the specific functions.

Adapted the dma_test domain to use the new interface.

DMA library: Bugfixes and missing implementations for IOAT

Moved the missing parts of the IOAT DMA driver into the library and
fixed some bugs in the initialization. Basic NOP descriptor test worked.

Also changed the channel get status queries to not accessing the device
register by default.

Changed the completion address reading to the memory region instead of
the register.

Added a new interface for IOAT DMA manager domain. (the driver domain)

Renaimed the scope of the error codes to DMA_ERR_*

LIBDMA: reorganized the header files.

LIB DMA: introduced generic parts of the structs (not fully done yet)