mmc: omap_hsmmc: Get rid of of_have_populated_dt() usage

of_have_populated_dt() is not expected to be used in drivers but
instead only in early platform init code.
Drivers on the other hand should rely on dev->of_node or of_match_device().
Besides usage of of_have_populated_dt() also throws up build error as below
which was reported by Balaji TK, when omap_hsmmc is built as a module.

ERROR: "allnodes" [drivers/mmc/host/omap_hsmmc.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

So get rid of all of_have_populated_dt() usage in omap_hsmmc driver and
instead use dev->of_node to make the same dicisions as earlier.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Reported-by: Benoit Cousson <b-cousson@ti.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Reviewed-by: Balaji T K <balajitk@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>