cpumask: kernel-doc cleanups and additions

Clean up some punctutation and abbreviations.
Add kernel-doc notation for one function and function return value
for 39 functions.

cpumask.h:
Fix some punctuation (plural vs. possessive).
Fix some abbreviations (ie. -> i.e., id -> ID).

Fix 35 warnings like this:
include/linux/cpumask.h:161: warning: No description found for return value of 'cpumask_first'

cpumask.c:
Add Return: value for 4 functions.
Add kernel-doc for cpumask_any_distribute().

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>