OMAP2+: hwmod: ignore attempts to re-setup a hwmod

Previously, if a hwmod had already been set up, and the code attempted
to set up the hwmod again, an error would be returned.  This is not
really useful behavior if we wish to allow the OMAP core code to setup
the hwmods needed for the Linux clocksources and clockevents before
the rest of the hwmods are setup.  So, instead of generating errors,
just ignore the attempt to re-setup the hwmod.

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