s390/sclp: Refactor sclp_cmd.c

s390/sclp: Refactor sclp_cmd.c

To improve readability, refactor sclp_cmd.c:
* Move defines and structures to the beginning.
* Reverse x-mas tree usage.
* Remove spaces after casting to eliminate checkpatch warnings.
* Remove unnecessary comments.
* Reframe certain comments.
* Convert all unsigned long long to unsigned long since unsigned long
  long is a leftover from the 31/32-bit era.
* Use correct format specifiers.
* Add braces to for loops with bodies containing more than one line.
* Sort header files and remove unnecessary ones.
* Use __packed and __aligned instead of __attribute((packed,
  aligned(8))) in structures.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>