HID: hidraw, uhid: Always report EPOLLOUT

HID: hidraw, uhid: Always report EPOLLOUT

commit 9e635c2851df6caee651e589fbf937b637973c91 upstream.

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: be54e7461ffdc ("HID: uhid: Fix returning EPOLLOUT from uhid_char_poll")
Fixes: 9f3b61dc1dd7b ("HID: hidraw: Fix returning EPOLLOUT from hidraw_poll")
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
[bwh: Backported to 3.16:
 - Use unsigned int type instead of __poll_t
 - s/EPOLL/POLL/g]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>