i2c: designware: Cleaning and comment style fixes.

The purpose of this commit is to fix some comments and styling in the
existing code due to the need of reuse this code. What is being made
here is:

- Sorted the headers files
- Corrected some comments style (capital letters, lowcase i2c)
- Reverse tree in the variables declaration
- Add/remove empty lines and tabs where needed
- Fix of misspelled word "endianness" and "transferred"
- Replaced the return variable "r" with the more standard "ret"

The value of this, besides the rules of coding style, is because I
will use this code after and it will make my future patch a lot bigger and
complicated to review. The work here won't bring any additional work to
backported fixes because is just style and reordering.

Signed-off-by: Luis Oliveira <lolivei@synopsys.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>