[ARM] pxa/spitz: Rework spitz

This huge patch mostly shuffles code. The spitz.c file contained terrible mess
and needed a cleanup, here it is:

1) Made every part modular, components are not built in if not selected.
2) Removed loads of preprocessor goo, mostly "#ifdef MACH_AKITA .... #endif" and
   similar code. The kernel size will grow by a few kb now, but the file is much
   more readable.
3) Reworked SD/CF power setting function and made it reentrant.
4) Add ISL6271A regulator support
5) Correctly register WM8750

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>