iop13xx: surface the iop13xx adma units to the iop-adma driver

Adds the platform device definitions and the architecture specific
support routines (i.e. register initialization and descriptor formats) for the
iop-adma driver.

Changelog:
* added 'descriptor pool size' to the platform data
* add base support for buffer sizes larger than 16MB (hw max)
* build error fix from Kirill A. Shutemov
* rebase for async_tx changes
* add interrupt support
* do not call platform register macros in driver code
* remove unnecessary ARM assembly statement
* checkpatch.pl fixes
* gpl v2 only correction

Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>