soc: qcom: ipa: main code

This patch includes three source files that represent some basic "main
program" code for the IPA driver.  They are:
  - "ipa.h" defines the top-level IPA structure which represents an IPA
     device throughout the code.
  - "ipa_main.c" contains the platform driver probe function, along with
    some general code used during initialization.
  - "ipa_reg.h" defines the offsets of the 32-bit registers used for the
    IPA device, along with masks that define the position and width of
    fields within these registers.
  - "version.h" defines some symbolic IPA version numbers.

Each file includes some documentation that provides a little more
overview of how the code is organized and used.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>