OMAP2+: hwmod: Fix what _init_clock returns

_init_clock always returns 0 and does
not propogate the error (in case of failure)
back to the caller, causing _init_clocks to
fail silently.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Acked-by: Benoît Cousson <b-cousson@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>