HID: hidraw, uhid: Always report EPOLLOUT

hidraw and uhid device nodes are always available for writing so we should
always report EPOLLOUT and EPOLLWRNORM bits, not only in the cases when
there is nothing to read.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: be54e746 ("HID: uhid: Fix returning EPOLLOUT from uhid_char_poll")
Fixes: 9f3b61dc

 ("HID: hidraw: Fix returning EPOLLOUT from hidraw_poll")
Signed-off-by: Jiri Kosina <jkosina@suse.cz>