chrt: (man,usage) put --pid first in synopses and examples, for clarity

chrt: (man,usage) put --pid first in synopses and examples, for clarity

When --pid is among the options, it is clearest when it is given as the
first option, because then it doesn't sit between the policy option and
the somewhat related priority value.  It creates some kind of symmetry:
the --pid option first, then other things, and the actual PID last.

CC: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Signed-off-by: Benno Schulenberg <bensberg@telfort.nl>