ARM: OMAP4+: hwmod code: remove clkdm requirement in _omap4_wait_target_*()

We're no longer requiring struct omap_hwmod records to contain a
clockdomain.  So we shouldn't return -EINVAL any more from
_omap4_wait_target_disable() or _omap4_wait_target_ready() if there's
no clockdomain defined, since that just gets passed back to the
caller.  This can result in pointless warnings under the relaxed data
format.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Benoît Cousson <b-cousson@ti.com>