omap_hsmmc: update struct hsmmc to accommodate omap3 from DT

This patch changes the way DM_MMC calculates offset to the base register of
MMC. Previously this was through an #ifdef but that wasn't necessary for OMAP3.

This patch will now add in the offset to the base address based on the
.compatible flags.

Signed-off-by: Adam Ford <aford173@gmail.com>

V2: Remove ifdef completely and reference offset from the omap_hsmmc_ids table.

V1: Change ifdef to ignore OMAP3
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>