ps: Output of nwchan is a number

ps: Output of nwchan is a number

For some time with enough compilier flags I have watched the
following warning drift by:
ps/output.c: In function ‘pr_nwchan’:
ps/output.c:658:41: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
   return snprintf(outbuf, COLWID, "%x", (unsigned)rSv(WCHAN_NAME, str, pp));

nwchan is supposed to be the address of where the process is sleeping,
not the name. Besides %x is a hex number not a string hence the warning.

nwchan now prints the address, in hex and GCC is happy.