rtc: rtc-max6902 fixes

- no changelogs in code
- no banners
- use local buffers
- fix probe sequence
- fixed style issues
- fix spi_write call
- removed old debug code

replaces http://patchwork.ozlabs.org/patch/9421/
and http://patchwork.ozlabs.org/patch/9455/

Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: David Brownell <david-b@pacbell.net>
Cc: Raphael Assenat <raph@raphnet.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>