pwm: Mark all devices as "might sleep"

Commit d1cd21427747 ("pwm: Set enable state properly on failed call to
enable") introduced a mutex that is needed to protect internal state of
PWM devices. Since that mutex is acquired in pwm_set_polarity() and in
pwm_enable() and might potentially block, all PWM devices effectively
become "might sleep".

It's rather pointless to keep the .can_sleep field around, but given
that there are external users let's postpone the removal for the next
release cycle.

Change-Id: I37237c2e04c171d29c2b4559aadcb36937b9d41e
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Git-commit: ff01c944cfa939f3474c28d88223213494aedf0b
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Krishnamurthy K R <kkr@codeaurora.org>